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Vectrino
Comprehensive Manual
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Nortek Vector, Vectrino, Vectrino Profiler Comprehensive Manual

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Page 1
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Comprehensive Manual2
Table of Contents
Chapter 1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
1.10
Chapter 2
2.1
Principles of Operation 7
Working Principle
Doppler Beams
Measuring Currents
Auxiliary Sensors
Measureme nt Volume
Coordinate System
Signa l Strength
Correlation
Distance Measurement / Bottom Check
Velocimeter Accuracy
.................................................................................................................. 8
Vector 1.5.1
.......................................................................................................................................................... 13
Vectrino 1.5.2
.......................................................................................................................................................... 14
Vectrino Profiler 1.5.3
.......................................................................................................................................................... 14
Using a Velocimeter 22
Vector
Technical description 2.1.1
.......................................................................................................................................................... 23
2.2
Vectrino
Instrument software 2.1.2
.......................................................................................................................................................... 25
Initial preparation 2.1.3
.......................................................................................................................................................... 26
Configuring a Vector 2.1.4
.......................................................................................................................................................... 27
Data Collection 2.1.5
.......................................................................................................................................................... 28
Mounting and Handling the Probe 2.1.6
.......................................................................................................................................................... 29
Orientation of Vector probes 2.1.7
.......................................................................................................................................................... 30
Measuring Waves 2.1.8
.......................................................................................................................................................... 31
Processing Method
Wave Parameters
Deployment Considerations and Cautionary Notes
Corrections, Measurement Errors and Uncertainties
Optional IMU 2.1.9
.......................................................................................................................................................... 35
Data handling 2.1.10
.......................................................................................................................................................... 36
Technical description 2.2.1
.......................................................................................................................................................... 37
Instrument software 2.2.2
.......................................................................................................................................................... 38
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Initial preparation 2.2.3
.......................................................................................................................................................... 38
Configuring a Vectrino 2.2.4
.......................................................................................................................................................... 39
Mounting and Handling the Probe 2.2.5
.......................................................................................................................................................... 41
Data Handling 2.2.6
.......................................................................................................................................................... 41
3Contents
Vectrino Profiler
2.3
Things to Consider
2.4
Technical description 2.3.1
.......................................................................................................................................................... 43
Instrument software 2.3.2
.......................................................................................................................................................... 44
Initial preparation 2.3.3
.......................................................................................................................................................... 45
Configuring a Vectrino Profiler 2.3.4
.......................................................................................................................................................... 45
Mounting and Handling the Probe 2.3.5
.......................................................................................................................................................... 46
Data Handling 2.3.6
.......................................................................................................................................................... 46
Probe Check 2.4.1
.......................................................................................................................................................... 47
Distance Check 2.4.2
.......................................................................................................................................................... 49
Velocity Ambiguity and Phase Wrap 2.4.3
.......................................................................................................................................................... 49
Extended Velocity Range 2.4.4
.......................................................................................................................................................... 50
Weak Spots 2.4.5
.......................................................................................................................................................... 50
Interference from Highly Reflective Bottoms 2.4.6
.......................................................................................................................................................... 52
Mooring Vibrations 2.4.7
.......................................................................................................................................................... 52
2.5
2.6
2.7
2.8
Chapter 3
3.1
Acoustic Streaming (Vectrino and Vectrino Profiler) 2.4.8
.......................................................................................................................................................... 52
Incorrect Speed of Sound 2.4.9
.......................................................................................................................................................... 53
Applications
Common Configuration Scenarios
Quality Assurance of Velocimeter Data
Common Data Analysis Scenarios
Mean Currents 2.5.1
.......................................................................................................................................................... 53
Low Flow Measurements 2.5.2
.......................................................................................................................................................... 54
Turbulence Measurements 2.5.3
.......................................................................................................................................................... 54
Laboratory environments 2.5.4
.......................................................................................................................................................... 54
Wave Measurements 2.5.5
.......................................................................................................................................................... 55
Near Boundary Measurements 2.5.6
.......................................................................................................................................................... 57
Service Manual 62
Function Testing
Initial Test Setup 3.1.1
.......................................................................................................................................................... 63
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Pow er
Converter
Connect cables
Start the appropriate softw are
Sensor Checks 3.1.2
.......................................................................................................................................................... 64
Temperature
Tilt or IMU (Vector)
Compass (V ector)
Pressure (Vector)
Noise floor 3.1.3
.......................................................................................................................................................... 67
Beam Amplitude and Velocity Checks 3.1.4
.......................................................................................................................................................... 68
Amplitude
Velocity
Probe Check
Test Recorder Function (Vector) 3.1.5
.......................................................................................................................................................... 70
Battery degaussing 3.1.6
.......................................................................................................................................................... 70
Customer Calibra tion
3.2
Working Inside an Instrume nt
3.3
Compass Calibration (Vector) 3.2.1
.......................................................................................................................................................... 70
Set Pressure Offset (Vector) 3.2.2
.......................................................................................................................................................... 71
Changing a Battery Pack (Vector) 3.3.1
.......................................................................................................................................................... 73
Accessing the Circuit Board (Vector) 3.3.2
.......................................................................................................................................................... 73
Installing a Memory Board (Vector) 3.3.3
.......................................................................................................................................................... 74
Installing a Memory Board - Pre-midlife (Vector)
Installing a Memory Board With Cable - Really Old Paradopps
Installing a DC/DC (Vector) 3.3.4
.......................................................................................................................................................... 76
Installing IMU sensor (Vector) 3.3.5
.......................................................................................................................................................... 76
Changing the Wiring Harness (Vector) 3.3.6
.......................................................................................................................................................... 77
Changing the Output Power for Auxiliary Sensors (Vector) 3.3.7
.......................................................................................................................................................... 77
Midlife Electronics
Pre-midlife Electronics
Changing a Probe
3.4
Upgrade Firmware
3.5
Erase Recorder (Vector)
3.6
Update Hea dfile (Vector)
3.7
Mechanical Aspects and Maintenance
3.8
Mechanical Tolerances 3.8.1
.......................................................................................................................................................... 81
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Instrument Care 3.8.2
.......................................................................................................................................................... 81
Recommended Torque for Securing Screws 3.8.3
.......................................................................................................................................................... 82
Connector Care 3.8.4
.......................................................................................................................................................... 82
Cable Care 3.8.5
.......................................................................................................................................................... 82
O-ring Care 3.8.6
.......................................................................................................................................................... 83
Replace Desiccant Bag 3.8.7
.......................................................................................................................................................... 83
Biofouling 3.8.8
.......................................................................................................................................................... 83
5Contents
3.9
Chapter 4
4.1
4.2
4.3
Cable s and Wires
Vector 3.9.1
.......................................................................................................................................................... 84
Vectrino 3.9.2
.......................................................................................................................................................... 87
Vectrino Profiler 3.9.3
.......................................................................................................................................................... 88
Using Long Cables (Vector) 3.9.4
.......................................................................................................................................................... 88
Harness (Internal wiring) 3.9.5
.......................................................................................................................................................... 88
Integrators Guide - Light 90
Analog Inputs (Vector)
Analog Outputs
Synchronizing w ith Other Instruments
Vector 4.2.1
.......................................................................................................................................................... 93
Vectrino 4.2.2
.......................................................................................................................................................... 93
Vector 4.3.1
.......................................................................................................................................................... 94
Vectrino 4.3.2
.......................................................................................................................................................... 97
Vectrino Profiler 4.3.3
.......................................................................................................................................................... 98
Chapter 5
5.1
© 2018 Nortek AS
Troubleshooting Guide 100
Communication Problems
.................................................................................................................. 101
Test with battery and power supply 5.1.1
.......................................................................................................................................................... 101
Cable Test 5.1.2
.......................................................................................................................................................... 101
Serial-to-USB converter 5.1.3
.......................................................................................................................................................... 102
Baud rate 5.1.4
.......................................................................................................................................................... 102
Serial COM port 5.1.5
.......................................................................................................................................................... 103
Break Response 5.1.6
.......................................................................................................................................................... 103
Loop Back Test 5.1.7
.......................................................................................................................................................... 104
Test with both RS422 and RS232 communication (Vector) 5.1.8
.......................................................................................................................................................... 105
Software 5.1.9
.......................................................................................................................................................... 105
Check Current Drain 5.1.10
.......................................................................................................................................................... 105
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Check fuse 5.1.11
.......................................................................................................................................................... 105
Check LED Indications 5.1.12
.......................................................................................................................................................... 106
Checksum Error 5.1.13
.......................................................................................................................................................... 106
Flash corrupt 5.1.14
.......................................................................................................................................................... 106
"Calibration matrix not stored" 5.1.15
.......................................................................................................................................................... 107
Instrument Stopped During Data Colle ction
5.2
Suspicious Data
5.3
Returning Instruments for Repair
5.4
Appendix A - Fina l Test Checklist
5.5
Appendix B - Example of Proforma Invoice
5.6
.................................................................................................................. 107
Power 5.2.1
.......................................................................................................................................................... 107
Full Recorder (Vector) 5.2.2
.......................................................................................................................................................... 107
.................................................................................................................. 108
Signal Strength 5.3.1
.......................................................................................................................................................... 108
Diagnostic Testing Using the Probe Check Function 5.3.2
.......................................................................................................................................................... 108
Boundaries 5.3.3
.......................................................................................................................................................... 112
Incorrect speed of sound 5.3.4
.......................................................................................................................................................... 112
Noisy Velocimeter Data 5.3.5
.......................................................................................................................................................... 113
Grounding Problems 5.3.6
.......................................................................................................................................................... 113
Phase Wrapping 5.3.7
.......................................................................................................................................................... 113
Mooring/mounting Vibrations 5.3.8
.......................................................................................................................................................... 114
Error and Status Codes (Vector) 5.3.9
.......................................................................................................................................................... 115
.................................................................................................................. 117
.................................................................................................................. 118
.................................................................................................................. 119
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1 Principles of Operation

This section covers
Basic Doppler principles Differences between the Velocimeters Current measurement and auxiliary sensors Measurement volumes Measurement method and measurement accuracy
Velocimetry is the measurement of the velocity of fluids. The name "Velocimeters" belong to a special class of high-resolution 3D instruments, that comprises the following instruments:
The Vector is a field instrument designed for measurements of rapid small scale changes in 3D velocity, used for turbulence, boundary layer measurements, surf zone measurements, and measurements in very low flow areas.
The Vectrino is used in hydraulic laboratories to measure turbulence and velocities in flumes and physical models. It also comes in a "field" version that has a more rugged design.
The Vectrino Profiler is a profiling version of the Vectrino. Its strength lies in its ability to collect data comprising of up to 30 cells that are only 1 mm in height.
Principles of Operation 7
Common for them is that they are typically used in difficult measurement situations such as turbulence measurements, very slow, low energy flows, and rapidly varying flows in the laboratory or the ocean. They can work well in areas with high shear, near boundaries, under breaking waves, and many other situations. Pulse coherent data from single or small ensemble average measurements are useful because of the individual measurement accuracy and low noise. In the following part, the concept of current measurements are divided into relevant topics.
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Figure : Trans m it puls e
pair (blue ), a moving
particle (red), and the
re flected, Doppler
shifte d puls e (black)

1.1 Working Principle

The Nortek instruments measure the velocity of water by utilizing a physical principle called the Doppler Effect. The Doppler Effect is the change in frequency of a sound wave when a wave source moves with respect to an observer, or when the observer itself moves relative to the wave source. You can hear the Doppler effect whenever a train passes by – the change in pitch you hear tells you how fast the train is moving.
There are many ways to measure the Doppler Effect, each with its own advantages and drawbacks. The Velocimeters measure velocity by transmitting a pair of short sound pulses of a specific frequency into the water column. Part of the sound wave reflects back to the instrument, the detected return signal will be further processed by the instrument. The reflected signal will be shifted ("Doppler Shifted") in accordance with the water velocity, which is what the processing is based on. More details about that will follow.
The sound pulses do not reflect from the water itself, but rather from passive tracers suspended in the water. These tracers or "scatterers" are typically zooplankton or suspended sediment that move with the same average speed as the water, hence measured velocities corresponds to the water flow. It is thus the moving particles that generates the change in pitch or frequency (the Doppler shift) in the return signal that the instrument measure at.
The Velocimeters utilize a pair of short acoustic pulses with a known time lag, or separation, to determine a Doppler induced phase shift. The use of two transmit pulses is commonly referred to as a pulse-to-pulse coherent method. By utilizing this method the instrument is able to differentiate relatively small differences in the velocities (corresponding to small differences in phase) and therefore achieving great accuracy (often able to achieve velocity variance orders of magnitude lower than standard incoherent Doppler systems) and low noise measurements. A limitation is the maximum profiling range.
The figure below visualize how a sound wave transmitted through the central transducer (shown in blue), hits a particle (red), which in next turn reflects parts of the sound (Doppler shifted - shown in black) and the slanted beam which is the receiver arm which will detect the reflected sound wave. Only one beam is shown for the sake of overview.
Water flows can be measured in many different ways, depending on how accurate the measurements need to be and how often the measurements need to be taken to detect the variation of interest. As described in the section above, the Velocimeters use sound waves and the Doppler
© 2018 Nortek AS
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Principles of Operation 9
Figure : Tw o pulses are tr ans m itte d by the centr al tr ans ducer, w ith a tim e lag. The differe nce in phase
betw ee n the tw o transmit pulse s is us e d to calculate velocity. The re flecting par ticle can be s e e n in
green, w ith a vector indicating its spe ed and direction
effect to measure velocity fluctuations underwater, and can do so several times per second. But exactly how does this transmission and receive of sound waves turn into velocity estimates?
Processing Technique
The phase difference between two transmit pulses is the basis for estimating current velocities using the pulse coherent processing technique.
The phase difference between the two reflected pulses is a direct measure of the velocity, and can be expressed as
Here, V is the current velocity, ∆φ is the phase difference, F_source is the transmitted frequency and ∆t is the time difference between two consecutive pulses ("Lag"). The V is scaled with the speed
of sound in the liquid (C).
There are some aspects with the pulse coherent method that affects what the instrument is able to measure.
The Doppler phase shift is computed using the covariance method. By computing the complex covariance of the two return signals, the Doppler phase shift can be calculated by taking the four quadrant arctangent (atan2 in most programming languages) of the real and imaginary parts of the
covariance function. This restricts solving the phase difference within the range of [-π, π]. The calculation of φ is beyond the scope of this manual, but the impact of using this method is
important. It introduces the problem of ambiguous determination of the phase shift; if the phase
difference goes outside the range of ±π, the measurement uniqueness is lost, something known as Velocity Ambiguity. For example, a sine wave with phase -π looks the same as a sine wave with phase π. Read more about this here; Velocity Ambiguity and Phase Wrap, but the take home
is that there is a maximum velocity the instrument is able to measure.
The size of the lag (∆t in the equation above) determines the maximum unambiguous velocity that
can be measured. Longer lags have lower maximum velocities, while shorter lags have higher maximum velocities. Conversely, longer lags will typically have higher velocity accuracy (lower noise levels) than shorter lags, but potentially degraded signal correlation due to particle advection
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Comprehensive Manual10
Figure : The blue arrow indicates a pos itive velocity.
and turbulence. It is therefore important to set the time lag properly. Information on what you need to think about when setting this parameter can be found in the Using a Velocimeter chapter. Near boundary measurements are prone to interference. This may happen if the first pulse is reflected from a boundary and reach the sampling volume on its way back at the same time as the second pulse is in the sampling volume. This is referred to as a Weak Spot.

1.2 Doppler Beams

All Acoustic Doppler Velocimeters send out short acoustic pulse pairs from the transmitter (center) element. When the pulses travel through the focus point for the receiver beams, the echo is recorded in each of the acoustic receiver elements and the phase shift between two consecutive is found. The phase shift is then processed to find the actual velocity of the water, as described in the previous section. The instrument samples on all three of four receivers simultaneously.
The Doppler shifts measured at the three or four receivers provide estimates of flow velocity along the different beam directions, which are then combined geometrically to obtain the three orthogonal components of the water velocity vector V (illustrated by the blue arrow in figure below). The Velocimeters are in this way able to calculate 3D water velocity in the sampling volume by knowing the exact orientation of the beams.
The Vector, which is shown in the figure above has three receiver arms, while the Vectrino and the Vectrino Profiler have four receiver arms. Because of the arrangement of the receiver arms, each pair (composed of two opposing receivers) can measure the horizontal velocity component and the vertical velocity component. Z1 and Z2 are the vertical velocity estimates associated with receivers 1 & 3 (X) and 2 & 4 (Y). For the standard downward looking probe, Z1 and Z2 are thus independent measurements of the vertical velocity. Note that the side-looking probe does not have a secondary measurement of the vertical velocity. Z1 will be the correct vertical velocity and Z2 should be output as zero.
All Velocimeters go through a probe calibration procedure during its production. This to know the exact geometry of the probe, and this information is saved in what we call head matrices. As long as the sensor heads are not physically deformed, the head matrices will, consequently, remain the same. This also means that the calibration only needs to be done once, and there is no need to re­calibrate the probe again - unless it has physically been deformed.
A bistatic system
Bistatic geometries have been used with intersecting narrow beams to produce a measurement volume in the intersection zone. A bistatic system is one where the transmitter and receivers are physically separated; the transmitter generates sound along the vertical beam, and the receivers listens for it. This results in motion along two axes, the component of motion of the object in the direction of the transmitter and the component of motion in the direction of the receiver. The motion
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Principles of Operation 11
Figure : The trans m it/re ce ive be am pair is sensitive to
velocity in the dire ction of the angular bisector betw een
the be am s .
can be considered as proportional to the rate of change along the bisector of the transmit and receive beams (indicated by the blue arrow in the figure below). Knowing the relative orientation of the bistatic axes and the receivers makes it easy to calculate 3D velocities. The receive beams are slanted 30°, thus the angular bisector is 15° away from the transmit beam.
The Z (vertical) and X- and Y (horizontal) velocity limits are tied fundamentally to the geometry and are not independent. The conversion from beam to XYZ coordinates has Z in the direction that the central transducer is pointing and XY is always orthogonal to Z. The "Vertical" and "Horizontal" velocity range is reported in the Deployment planning dialog. The reason that the Vertical range is so much lower than the Horizontal velocity range is because of the angle used by the passive receivers (30 degrees). This makes the projection of the passive beams onto the horizontal plane about ~1/4 (sin(15)) (so the maximum horizontal velocity measurable is ~4x the maximum beam velocity) while the projection of the passive beams onto the vertical plane is 0.96 (cos(15)) (so the maximum vertical velocity is pretty much the same as the maximum beam velocity). Consequently, the Z-velocity component yields a lower measurement uncertainty.
In other words, for best measurement, you should always have the largest component of speed in the horizontal plane from the point of view of the transducers. On another note, even if you do reorient the probe, when operating at that current, you will likely still have to watch out for wraps in the velocities if there are any local eddies occur which result in the beam ambiguity velocity being exceeded.

1.3 Measuring Currents

The processing technique described above is used because the measurement of a phase shift is more accurate than direct Doppler frequency determinations and provides pulse coherent systems with their characteristic low noise measurements. The instrument reports the phase shift converted to an along beam velocity by utilizing the speed of sound in water and the velocity data is output in m/s.
The user can specify which coordinate system to present the velocity data in. The raw velocity measurement is a vector in the direction along each of the three or four beams, which is referred to as beam coordinates. Beam coordinates can be converted to a Cartesian coordinate system (XYZ) by knowing the beam orientation. Furthermore, the flow can be presented in Earth normal coordinates (ENU- East, North and Up). In order to get the information referenced to earth coordinates (ENU - East, North, Up) it is therefore necessary to detect the instrument’s orientation in space. Attitude sensors, such as magnetometer and tilt are therefore used to aid in the transformation needed to correct for the instrument’s attitude and motion. The definitions of the coordinate systems are presented here: Coordinate System
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Comprehensive Manual12
The decision on which coordinate system to use should be based on what the aim with the data collection is. When handling data, XYZ or ENU coordinates are the most practical for a user. Beam coordinates are used when dealing with ambiguity (phase wrapping) and higher order turbulence calculations, as these are the "rawest" format.
Along with determining a phase shift (and then the velocity vector), the instrument will also typically compute the speed of sound, measure the return signal strength, and measure the attitude sensors such as pitch, roll, and compass heading (if equipped). For more about this; check the auxiliary
sensors section.
To assure high quality velocity data from a Velocimeter, it is important to configure it properly. The specifics for each instrument version is described in Using a Velocimeter.

1.4 Auxiliary Sensors

Along with determining a phase shift, the instrument will also typically compute the speed of sound (needed to change the phase shift to an actual velocity) and measure the return signal strength (reported in arbitrary units as counts and output as the variable Amplitude). Vectors also measure the attitude sensors such as pitch, roll, and compass heading (if equipped) to aid in the last step in processing; coordinate system transformation.
Pressure (Vector)
The pressure sensor measures the hydrostatic pressure and reports in units of dBar. Vectors sample pressure at the same rate as velocity.
The instrument do not set the pressure offset automatically, so this must be done using the software right before deployment to corrects for local atmospheric pressure. For more about this, check out the Service Manual. Note that a Nortek pressure sensor cannot measure negative values.
Temperature
The instruments use the speed of sound to convert time to distance and Doppler shift to velocity, and since speed of sound depends on temperature, the data from the temperature sensor is of vital importance. The temperature is measured by a thermistor embedded in the probe and reported in degrees Celsius. The instruments sample temperature every second. The time response is about 10 minutes for the Vector, 5 minutes for the Vectrino and the Vectrino Profiler.
Magnetometer and Tilt (Vector)
The Vector compass is a system including a 3-axis magnetoresistive magnetometer, a liquid tilt sensor, algorithms to convert data from these sensors into heading and instrument tilt, and a calibration algorithm. The magnetometer measures the magnitude of three components of earth's magnetic field, and the tilt sensor measures two components of tilt and detects up/down orientation. The Vector (with compass) combines this information to compute the instrument's tilt and heading, then uses the tilt and heading to correct measured velocities to ENU coordinates.
Tilt sensor: The tilt sensor measures the orientation of the instrument and comes in two versions; vertical orientation and horizontal orientation. The tilt sensor is calibrated within +/- 30º, but the accuracy is significantly better for smaller tilt angles because of the technology used to measure tilts.
If an instrument with vertical orientated tilt sensor is to be mounted horizontally, the tilt sensor data will be un-useable and the data would need to be collected in XYZ or BEAM coordinates. It is possible to change the orientation of the sensor, but the instrument would need to be returned to Nortek. In addition to the physical replacement of the instrument would need to go through calibration.
The tilt sensors measure tilt relative to earth gravity. If the instrument is moving (e.g. when mounted on a buoy), the tilt sensor cannot differentiate the acceleration from the buoy from the acceleration of
© 2018 Nortek AS
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Principles of Operation 13
Figure : The Ve ctor beam s inte r s e ct e ach othe r at a know n
distance fr om the cente r tr ans ducer, defining the
measurement volum e .
gravity. We therefore offer the Vector with an integrated IMU (inertial measurement unit) which operates over a larger tilt range and can be used to correct measurements for motion contamination.
This sensor is intended to help understand how the Vector's own motion influences the measurements. The simple configuration allows one to basically record motion data simultaneously with the Vector velocity data. Physically, the IMU is incorporated in the Vector by simply using the magnetometer contact interface. This means the standard tilt and magnetometer are removed and replaced with the IMU, so there is no standard Nortek compass system with the IMU integrated. More about this sensor can be found here: Optional IMU.
Magnetometer: Magnetoresistive (MR) magnetometers sense magnetic fields with thin strips of a metal alloy whose electrical resistance varies with a change in applied magnetic field. These sensors have a well­defined axis of sensitivity. The Vector's compass includes three MR sensors, one each for X, Y and Z components.
Each compass system is calibrated at the factory to quantify the characteristic response of the individual components and of the system as a whole. When it leaves the factory, each system can measure its tilt and the direction of its magnetic field vector accurately, anywhere in the world.
Note: Users disturb the magnetic field near the instrument when they deploy. Adding a battery pack and mounting the instrument with deployment hardware adds magnetic materials that change the magnetic field measured by the instrument. The compass calibration procedure quantifies this magnetic disturbance, and the instrument's compass algorithm then corrects for it to obtain accurate heading.

1.5 Measurement Volume

The Velocimeters use separate transmit and receive beams and are therefore referred to as bistatic sensors. The measurement volume is defined by the intersection zone of the three or four slanted receivers and the central transmitter.

1.5.1 Vector

The Vector measurement volume is defined as the area where the beams intersect each other, that is, 157 mm from the transmitter. The transmit transducer sends a short pulse that covers only about 4 mm vertically (user selectable), and the receivers listen to an echo that corresponds to about 14 mm vertically (also user selectable). Since the Vector use three receivers, all focused on the same volume, it obtains three simultaneous velocity measurements from that very volume.
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Comprehensive Manual14

1.5.2 Vectrino

The Vectrino measurement volume is defined as the area where the beams intersect each other. For the Vectrino that is 5 cm from the transmitter, for the Vectrino field probe, it is 10 cm. The transmit transducer sends a short pulse that covers 3-15 mm vertically (user adjustable), and the receivers listen to an echo that corresponds to this volume (see figure below). The diameter of the volume is 6 mm.
The Vectrino side-looking probe (figure below, middle) has two horizontal beams and two slanted 65° from the vertical. The two horizontal beams measure the U and V velocity. This means that the data from the two slanted beams are not required when measuring horizontal velocity, and the side­looking probe then act as a 2D system. This means that this probe can be used in really shallow water applications, as only the two horizontal beams need to be submerged to get 2D velocities. Side-looking probes do not have the problem of weak spots, so they are a little more robust to operate, especially in high flow environments. Due to the design, the side-looking probe has higher instrument noise in the vertical than in the horizontal.
The Vectrino be am s interse ct each othe r at a k now n distance for m the cente r tr ans ducer, defining the
measurement volum e . The V e ctr ino to the left is the dow n-looking version, the one in the m iddle is a so-
called s ide-look ing proble , and the fie ld probe is presente d to the right.

1.5.3 Vectrino Profiler

The mechanical and acoustic characteristics of the Vectrino and the Vectrino Profiler are identical; both employ the same probe assembly and transducers. However, the Vectrino Profiler provides for profiling over a 30 mm range interval thereby allowing measurement of the spatial structure of the flow (see figure below).
The figure above shows how the beams intersect each other 50 mm from the transmitter. The measurement profile is defined by this intersection and by range gating in time. Four passive transducers, angled at 30° towards the center surround the central active transducer, allowing 3D velocity measurements. With a profiling range up to 30 mm, a usable profiling region approximately 40-70 mm in height from the central transducer is provided. The Vectrino Profiler pulse intervals are longer than the Vectrino because of the need to sample data from farther away.
© 2018 Nortek AS
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1.6 Coordinate System

Figure : Coordinate s ys te m s. From left: Beam coor dinates, XYZ coordinates and ENU coordinates
You may specify the preferred coordinate system in the Deployment Planning menu of the instrument specific software. The velocity measurement is a vector in the direction of the transducer beam, which we refer to as beam coordinates. Beam coordinates can be converted to a Cartesian coordinate system (XYZ) by knowing the beam orientation. Furthermore, the flow can be presented in Earth normal coordinates (ENU - East, North and Up) if the instrument is equipped with a compass and tilt sensor.
The coordinate systems are defined as follows:
In Beam coordinates, a positive velocity is directed in the same direction as the beam points. Beam 1 is defined as the arm with the black / red marking. If the marking is missing, beam 1 can be identified as the arm opposite of the engraved serial number on the probe. Beam velocities are not corrected for probe geometry. In XYZ coordinates, a positive velocity in the X-direction goes in the direction of the X-axis arrow. The X-axis points in the same direction as beam 1, and newer models have the direction engraved in the probe endbell itself. Use the right-hand-rule to remember the notation conventions for vectors. Use the first (index) finger to point in the direction of positive X-axis and the second (middle) finger to point in the direction of positive Y. The positive Z-axis will then be in the direction that the thumb points. Remember that XYZ coordinates are relative to the probe head and independent of whether the instrument points up or down. For instruments with 4 receiving transducers, an extra Z velocity is outputted (X, Y, Z1 and Z2). In ENU coordinates, a positive east velocity goes toward east. This is also a right-handed orthogonal system.
Principles of Operation 15
ENU and XYZ coordinates are the most practical when handling data. Beam coordinates are primarily useful for higher-level turbulence calculations and for dealing with phase wrapping issues.
The figure below shows an assortment of Velocimeters probes and the definitions of beam and XYZ coordinates.
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Figure : The Ve ctrino/Vectrino Profiler and Vector XYZ coordinate s ys te m s and beam numbe ring as
define d re lative to the probes. Beam 1 of the Ve ctrino has a re d mark ing, a black mark ing de fines beam 1
for the Ve ctor (not show n here). For the Ve ctor, beam 1 is als o the arm opposite of the e ngraved head ID.
Be am 1 point in the dir e ction of positive X-axis. The Y dire ction can be found in accordance w ith the
right-hand r ule .
Counts
For signal strength, Nortek frequently make use of the word counts, which obviously seem to be connected to the decibel term, but how and why?
Inside the velocimeters there are circuitries for the amplification of input signals. The number of counts is an indicator of how much gain we must apply to a signal – the less gain needed, the higher the input signal level is. The number of counts is inversely proportional to the logarithm of the gain setting, which means that a higher number of counts reflects a need for less amplification than a lower number of counts will do.
Strong signals have a higher noise immunity and they correlate much better than weak signals do. For the Vector, 1 count ~ 0.4– 0.45 dB.
For the interested reader: For the Vector probe (see illustration third to the left, lower part), one may notice that the X component is predominantly measured by beam 1 with nearly equal contributions from beam 2 and beam 3. This makes sense since the XYZ coordinate system is aligned with X
pointing along one receiver arm. Beams 2 and 3 are at some angle α to the X-axis and measure a component of X proportional to cosα. For the Y-component, beam 1 contributes to zero (or very near
zero) because the Y-component is perpendicular to beam 1. Finally, the Z component is an equal combination of all three beams since the Z-axis is aligned with the central transducer and each beam is at the same angle to the Z-axis. Note that this concept applies to the other probes as well.

1.7 Signal Strength

To be confident about the quality of the data and allow proper calculation of the velocities, the received echo (reflected by particles) need to be over a certain level. Signal strength (amplitude) is a measure of the magnitude of the acoustic reflection from the water, and is a function of type and amount of particles in the water. If the echo is weak, the calculation will be statistically "noisy" and the velocity data will show significant short-term variability. Signal strength is outputted by the instrument and can be used to assess data quality.
The signal strength is accessed as raw signal amplitude (using dimensionless unit called Counts) or as a "Signal-to-Noise ratio", SNR (in dB).
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SNR
The Signal-to-Noise ratio (SNR) is defined as
SNR is displayed for each receiving beam. It is a measure of the level of the signal with reference to the background noise level. Strictly speaking, we are unable to measure the signal without the noise present, so Amplitude_signal should read Amplitude_signal+noise. However, for SNR values in the magnitude applicable to typical Velocimeter situations, the difference is negligible.
Figure : Signal to Noise Ratio from one V e ctr ino Profiler be am . A fixed boundary can be seen at about 6cm
from the trans m itter
The particles that is necessary to generate reflections of the acoustic signal can be naturally occurring suspended sediments (rivers, ocean, sand-filled or polluted model basins), bubbles entrained from pump systems (often the case in flumes), or artificial ("seeding").
When measuring in basins or flumes, seeding is often needed. If practical, we recommend that stagnant, clear basins or flumes are seeded with hollow spheres that have a density close to that of
water and a size around 10 µm. Particles that are close to neutrally buoyant will remain in
suspension without additional stirring and are ideal for low-flow experiments. The choice of size is motivated by the relatively strong echo that these particles generate per unit of concentration.
Smaller particles (e.g. 1 µm particles used to seed Laser Doppler systems) are not recommended
because the required concentration is quite high.
When collecting raw data (e.g. at 25 Hz), we recommend an SNR that is consistently above 15 dB. When collecting mean data (for example, 10 second averages), we recommend an SNR of at least 5 dB. If the SNR remains low even after seeding, try to clean the receive and transmit transducers by gently rubbing the surface with a finger. This will clean off residues or bubbles that may have collected and are blocking the sound. Take a look at the Troubleshooting Guide for more about how to increase SNR.
The determination of the quality of the data is the primary use of the signal strength, for the Vectrino Profiler it also determines the range over which the instrument can measure velocity accurately. It may also be used to retrieve information about the suspended sediment or the concentration of the scattering materials. Note that different types of scattering elements produce different echoes, and it is difficult to distinguish between conditions with few, relatively big scattering elements or many small elements. For users interested in sediment concentration estimates it is recommended to take a look at this subject in the Frequently Asked Questions (FAQ) on the Nortek web.

1.8 Correlation

© 2018 Nortek AS
Correlation is a measure of the similarity of the two pulse echoes being measured. Zero correlation means nothing at all is similar between the two echoes, and a correlation of 1 means the two echoes are identical. The number reported by Nortek instruments is a normalized correlation value and will always lay in the interval 0-100%. The aim is high correlation because it gives confidence the system measured the two pulses it originally sent out and is determining a valid phase shift. In practice we
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Figure : Corr e lation from one Vectrino Profiler beam . This plot cor responds to the SNR figur e in the
previous section. Note how the boundary s how s up in this plot
will never see correlations of zero because of noise due to electronics, temperature fluctuations, and other factors that will always correlate above zero.
Discarding measurements with correlations lower than a threshold significantly reduce the variance of the data set, which is generally the goal of most data screening operations. Removing low correlation measurements is still a good idea because correlation is a strong indicator of data quality in the sense of a valid Doppler phase shift determination. However, high correlation is not always indicative of a valid measurement of the flow. It is also important to note correlation is tied to a specific beam velocity measurement, not to an orthogonal coordinate direction such as X, and any screening should take this into account.
In the early days of the acoustic Doppler velocimeter, if a user did some tests and determined correlations were above ~70% then the instrument was considered to be generating good quality data. Many users still use this number for screening out bad data, although a generalization to some universal value is unwarranted and a close examination of the dataset is the best way to set a correlation threshold (if any) for discarding bad data points.

1.9 Distance Measurement / Bottom Check

The distance check (also referred to as Bottom Check) is used to measure the distance to the bed from the central transducer. The return from this pulse is listened to over some time to obtain an amplitude profile. The amplitude profile is checked for peaks, and an interpolation scheme is used to locate the peak location based on the largest amplitudes recorded.
The Distance Check function is available in the Vectrino Plus firmware, the Vector and the Vectrino Profiler, but not in the Vectrino standard firmware.
Vector: The Vector reports the distance to the boundary at the start and end of each burst, or at the start when running the instrument in Continuous mode. That means that it is possible to do very short bursts and get almost simultaneous measurements (requires Firmware V1.20 or higher).
Vectrino Plus: The Vectrino+ firmware comes with a separate boundary distance mode (10 Hz), where the distance to the boundary is measured. The distance measurement is not done at the same time as the velocity measurements. The Boundary Distance functionality is typically used in experiments where bottom changes as a function of time are needed, or when the Vectrino+ is mounted on traverse systems for bottom topography measurements.
Vectrino Profiler: The Vectrino Profiler has an interleaved boundary distance functionality. In other words, you get both velocity profiles and distance to the bottom at the same time. The reasons for this are both that it can be done technically, and also that the problem of weak spots is much more challenging with the Vectrino Profiler than with a single point instrument. Hence, in order to operate the Vectrino Profiler properly we depended on interleaving velocity and distance measurements, such that the time lag between the two pulses in every pulse pair can be adjusted adaptively.
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Principles of Operation 19
Measureme nt range:
The maximum and minimum distances that can be measured are approximately as listed below, but note that it will depend a lot on the hardness of the bottom.
Vector: 4 cm - 45 cm Vectrino+: 1 cm - 35 cm Vectrino Profiler: 20 mm - 2 m. The Vectrino Profiler can be configured where to start collecting bottom check data. Refer to SW user guide (available within the software) for more details.
We provide all of the data used to determine the peak location if users need to create their own bottom detection algorithm. This is available as the probe check data in the Vector and Vectrino, and in the Bottom Check fields in the Vectrino Profiler data structure.
Quality (relevant for Vectrino Plus)
Quality is a number indicating how valid the distance measurement is. Above 100 should be a good distance measurement. It is always good to have an independent estimate of position though, so we usually recommend using the probe check feature of the Vectrino software to get a ballpark number.
More information about the Distance Check can be found in the Using a Velocimeter chapter.

1.10 Velocimeter Accuracy

The word accuracy is often used loosely to cover some combinations of bias and short-term uncertainty. Bias and short-term uncertainty are different, and they have different ramifications for the results of your data collection. Here is the difference:
Bias is error that remains after taking long-term averages. Short-term error is the random error of individual measurements, which can be removed by averaging.
These errors have different sources and different consequences for the results. The following will address each of these errors separately.
The velocity measurements are the average of many velocity estimates (called pings). The uncertainty of each ping is dominated by the short-term error. This error is uncorrelated from ping to ping, so by averaging together many pings, the measurement uncertainty is reduced. The short-term error depends partly on internal factors, such as the size of the transmit pulse, the measurement volume and the beam geometry. Beams parallel to the dominant flow will have smaller short-term errors than beams at a steep angle relative to the flow.
The instrument’s software predicts errors based on the short-term error of a single ping and the number of pings averaged together. Averaging multiple pings reduces errors according to the formula:
Where σ represents the standard deviation and N is the number of pings you average together. Note
that the software predicts only the instrumental error.
In many situations, external factors such as the environment itself dominate the short-term error. This is true near an energetic surface and in turbulent flow such as boundary layers and rivers. In situations like this, your data collection strategy should take into account the nature and the time scales of the environmental fluctuations. Here are two scenarios:
Example: Waves. When measuring mean velocities in the presence of waves you should sample velocity at roughly ¼ the interval of the dominant wave period, and you should sample through 6-10
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wave cycles. Example: Turbulent flows. In boundary layers, a rough rule of thumb is that the root-mean-square (RMS) turbulent velocity is 10% of the mean velocity. If, for example, your mean velocity is 1 m/s, you could estimate turbulent fluctuations to be 10 cm/s. Obtaining 1 cm/s RMS uncertainty would require at least 100 pings.
When averaging several pings to reduce the error, there is a difference between the resulting “mean current” and the measured current. This deviation from the actual current measurement is called bias . Velocimeter bias depend on the geometry of its probes and the stability of its internal oscillators. Over most of the velocity range, bias can be measured in terms of an offset and a scale-factor error. Offsets would appear as a non-zero velocity in still water. If probe geometry were entirely fixed and repeatable, then we could determine the velocity scale factor based entirely on dimensions, frequencies and our physical model. In practice, small variations in probes require that probes are calibrated individually in the factory.
A factory-calibrated velocimeter should have a scale-factor bias that is less than 1% of the measured velocity. A velocimeter will retain this accuracy as long as its probe remains unbent.
Bias increases near the extremes of a velocimeter's velocity range because velocities that would be measured beyond the extremes wrap around to the opposite end of the range. This can be avoided by keeping the maximum observed speed toward the middle of the velocimeter's maximum range. The configuration parameter to adjust is the Velocity Range.
Uncertainty, variance and standard deviation
Uncertainty is often measured in terms of measurement variance or standard deviation. These two are related:
variance = (standard deviation)^2
Standard deviation quantifies the amount of variation of a set of velocity values, around the true value of the velocity. For example: Imagine taking measurements of an unvarying velocity. The best estimate of the true velocity is the mean of the measurements, and the uncertainty of each of the measurements is the standard deviation of the collection of measurements.
Averaging
When averaging a collection of velocity measurements, the average is a better estimate of the true velocity than each individual estimate. The uncertainty of the average is reduced according to:
variance(mean) = variance(individual measurements)/N
std dev(mean) = std dev(individual measurements)/N^1/2
In other words, by reducing the variance of individual measurements by a factor of 2, you can collect data twice as fast.
Measureme nt Loa d (Vector)
A 100% measurement load means that the instrument pings as fast as it is able to. Consequently, a measurement load of 50% means that the instrument pings at half that rate. From signal theory we know that the more pings there are within an averaging period, the better the estimate of the true value we are measuring will get. By increasing the measurement load, the precision in the velocity measurements increase, but alas at the expense of battery consumption. By decreasing the measurement load it is the other way around.
The measurement load for the Vector is adjusted according to the velocity range selected.
Variance and Noise Level
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Principles of Operation 21
The velocimeter's noise level, also called the noise floor, is its most fundamental measure of measurement uncertainty. If the noise level is known, one can easily compute the expected variance or standard deviation of the measurements for any sample rate. Velocimeter uncertainty is a random white noise. This means that each velocity estimate is independent of the next, and it means that the noise has no preferred frequency.
The noise level varies widely according to the characteristics of the velocimeter, how it is set up, the characteristics of the flow, and the acoustic scattering environment. Here is how the noise level and measurement variance are related:
variance = (noise level)*(sample rate)/2
By using the equation in the "Averaging" section, the equation above can be turned into an equation for standard deviation.
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2 Using a Velocimeter

This section covers
What you need to know when using a Vector What you need to know when using a Vectrino and/or a Vectrino Plus What you need to know when using a Vectrino Profiler Measurement scenarios, and what you need to think about when configuring the instrument for these scenarios General operational considerations, common configuration problems and common data analysis scenarios
The Velocimeters bear lots of similarities, and this section is trying to separate the instruments from each other at the same time as covering subjects that are relevant for them all.
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2.1 Vector

Using a Velocimeter 23

2.1.1 Technical description

For technical specifications, check out the product on our website.
Probe with Transducers
The probe is mounted either on a cable or a fixed stem connected to the main housing through the probe endbell. The probe consists of three receiver transducers, each mounted inside a receiver arm, and a transmit transducer at the center. When an instrument uses separate transmit- and receive transducers, it is called a bistatic sensor.
The center transducer transmit the sound waves, and the three receivers listen and measure the Doppler shifted return signal.
Pressure Sensor
The Pressure sensor is located inside the probe endbell. The pressure sensor provides instrument depth data, and can also be used for wave measurements.
The pressure sensor is not calibrated to, or corrected by the atmospheric pressure. This means that the pressure sensor reading will follow the atmospheric pressure. Therefore, a pressure offset should be run before using the instrument, and this can be done using the Vector software; click Menu: 'On­line' - 'Set Pressure Offset...'.
The pressure sensor offset should be run right before the instrument id deployed. The pressure offset corrects for local atmospheric pressure, so by definition we want the pressure sensor to read zero in the air. If there were not large changes in atmospheric pressure relative to the current pressure offset, or the pressure sensor sensitivity was less than any atmospheric pressure changes, then the pressure sensor will read zero in the air.
The pressure data is collected at the same rate as velocity, which is set by the user in the Deployment Planning under Sampling Rate. That means that it can sample at up to 64 Hz.
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Because conversion from pressure to depth becomes quite complex as you move down below 500 m, we have included the full UNESCO calculations of depth as a function of pressure depth, salinity, temperature.
Temperature Sensor
The temperature sensor is located inside the probe endbell. The temperature sensor provides data on the water temperature, and is used for computing the Speed of Sound. Speed of sound can be set by the user (Fixed) or calculated by the instrument based on the measured temperature and a user­input value for salinity (Measured). The salinity is 0 for fresh water and typically 35 for the ocean.
The temperature sensor samples at 1 Hz.
Tilt Sensor
The tilt sensor is mounted on a small round PCB board attached to the probe. It is normally aligned parallel to the axis of pressure case axis for vertical operation. It can, however, optionally be installed perpendicular to the pressure case axis for operation with the pressure case horizontal.
The tilt sensor works equally well with the instrument pointed up or down. Note that when using the Vector in Continuous mode, only the very first measurement includes orientation information. If the Vector is oriented the opposite way during continuous data collection, the tilt sensor will not detect the change.
Tilt data is sampled at 1 Hz. The measurement range is +/- 30 degrees.
Is there uncertainty about whether the Vector has a vertical or horizontal tilt sensor? If the tilt (pitch and/or roll) as indicated in the Sensors’ pane is unrealistically far from 0° when placing the canister (upright or lying down) on a table, the Vector is of the other type.
Compass
The compass is located inside the pressure case, and measures the earth’s magnetic field. Combined with the tilt sensor on the head, the compass enables the Vector to obtain the heading. Without a compass, the Vector can still measure tilt. The compass enables the Vector to convert velocity measurements to Earth (ENU) coordinates.
Compass data is sampled at 1 Hz.
IMU sensor (Optional)
Nortek offers the Vector with an integrated Inertial Motion Unit (IMU). The IMU sensor is an electronic device that replaces the Compass board on the standard Vector. This sensor measure acceleration, angular rate and magnetic field along three axes. It is a valuable data source for applications where the instrument moves. Using an IMU with the Vector allows one to basically record motion data simultaneously with Vector velocity data. IMU data is sampled at the same rate as velocity. Note that there is no advanced internal processing.
Electronics Module
The electronics module is located inside the pressure case, and is a single board that holds the power transmitter, analogue and digital signal processing, power conditioning and the standard data recorder.
Power & Communication Cable
The power and communication cable is mounted to the endbell connector. The cable supplies external DC power and connects an external computer to the Vector for 2-way serial communication.
Cable Wiring is presented here: Cable Wiring. The Vector comes standard with an 8-conductor connector and cable.
External power
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Using a Velocimeter 25
You may supply power with the external supply that is delivered with the systems, or you can use your own external supply. If using your own supply, make sure the voltage does not exceed the voltage specification for the instrument.
The power and battery lines are diode protected, so you do not have to worry about wiring the instrument power backwards - this will not damage your instrument.
Vector power range: DC input 9-15 VDC
If you want to use an internal battery as a backup battery: The instrument will pick the power source with the highest Voltage. If using an external supply of 15 VDC and an internal battery of 13.5 V, the external supply provides a higher voltage than the battery pack, which prevents the internal pack from discharging. Then, if external power fails, the internal battery pack takes over and sustains operation.
Interna l batterie s (optional)
The internal battery pack is located inside the pressure case, and enables autonomous (stand-alone) deployments. It also provides backup power in the event of failure of the external supply. Note that the battery pack inside the pressure case is disconnected when sent from Nortek.
Nortek alkaline battery packs use 18 AA cell batteries at a nominal starting voltage of 13.5 VDC. The voltage of alkaline batteries falls quickly at the beginning, slowly during most of its life, then again quickly at the end. Thus, a 13.5 VDC battery pack will spend most of its life somewhere in a voltage range of 10.5-12.5 VDC.
Refer to the Changing a battery pack section for instructions on how to connect or change a battery pack.
The Vector power and/or battery lines are diode protected wiring the Vector power backwards will not damage your instrument.
Interna l Hardwa re (Electronics Module)
The signal processing hardware generates the signal that is converted to acoustic energy at the transducers, it digitizes the return signal and runs the Doppler processing that results in velocity estimates before it is outputted to the recorder or to a PC.
Recorder
The instrument comes standard with a 9MB recorder. There are options for 4 and 16GB recorders.
Additional Fratures
Analog inputs and Synchronizing Vectors

2.1.2 Instrument software

The software is designed to aid in the planning, execution, recovery and exporting data of stand­alone Vector deployments. It also contains an on-line section, including all functions required to operate the Vector in real-time applications. The Vector program can be found on the flash disk that came with the instrument, or on the Nortek web site: www.nortekgroup.com/software. Nortek Windows programs run on all versions since XP (SP3), including Windows 8.
Software Help: An on-line help system is integrated in the software; containing answers to all questions you may have on how to use the software. Click Help > Help Topics.
It is emphasized that the Vector program is not primarily designed for rapid data collection at high sampling rates or for controlling multiple Vectors. For these types of measurements, we instead recommend using CollectV for Vector.
Installing the Vector PC Software
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1. Insert the Flash disk, or find the Vector.exe on the web site.
2. Follow the on-screen instructions, accept the default settings. The Setup program will by default install the application in the c:\Nortek\Vector folder and create an application shortcut in the Nortek programs folder and on the desktop.
3. Restart your PC if prompted to, to finalize the installation process.
Communication with the instrume nt
Connect the instrument to one of the computer serial ports, using the Serial-to-USB adaptor. Select Serial Port from the Communication menu to specify the port number to use. It is recommended to accept the default baud rate settings - which is also the default instrument baud rate.
To check the instrument communication and verify that the instrument is connected, select Connect from the Communication menu or click the corresponding toolbar button. A message box with an identification or status string will pop up. Alternatively activate the Terminal Emulator window and press the send break button to send a BREAK signal over the serial port. A break causes the instrument to report an identification or status string. If it is not responding, or it responds with something unexpected, check the Troubleshooting chapter.
Changing the Baud Rate
There are two baud rates that can be specified in the software; communication baud rate and Recorder/firmware upgrade baud rate. A higher baud rate speeds up large file trasfers and is appropriate when you have a short serial cable and a relatively noise-free environment.
The standard baud rate is 9600. However, for 64 Hz data collection, you will need to use 19 200 baud.
To change the baud rate and make it permanent, do the following: 1 Connect the Vector to your computer. 2 Set the baud rate in Communication > Serial Port to the baud rate you prefer.
3. Press Stop Data Collection. The software will change the baud rate and make it permanent.
If you remove power and reapply it, the Vector will re-awake with the new baud rate.
Note! If data download is interrupted, the Vector may be left with a baud rate setting other than the one used for normal communication. When the software tries to establish communication in such cases, it may spend a few moments searching for the correct baud rate to use.

2.1.3 Initia l preparation

We recommend the following procedure to prepare the Vector for successful operation:
1. Verify that you have received all parts by using the Content of Shipment document that came with the instrument as a reference.
2. Install the internal battery pack.
3. Install the Vector Software on a PC.
4. Before a deployment it is recommended to run a functional test as described in the Service
Manual to verify that the instrument is functioning as intended and thus avoiding using a
malfunctioning instrument during deployments.
5. When you are ready to make your measurements, mount the Vector in accordance with the guidelines presented in Mounting and Handling the Probe. When deploying an instrument in the field, the primary goal of any deployment is to keep the mooring at the chosen location and to make as accurate measurements as possible.
6. We recommend starting a deployment with fresh batteries. If you are using an internal and external battery the primary battery will be selected based on which has highest voltage.
7. Verifying performance prior to the actual deployment can be a good idea to verify that the configuration works well and that you are going to record meaningful data before deploying the Vector and leave it on its own. For this you may use the data collection mode.
8. Do not forget to erase any data recorded by the Vector before the deployment is started, if storage
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capacity is crucial. We recommend starting new deployments with an empty memory.
Figure : Sampling seque nce w hen an ins trum e nt is configured for Burs t s am pling, w ith 600 se c burst
inte rval, 300 sam ple s at 1 Hz
9. For stand alone systems, it is vital to remember to connect the dummy plug to protect the connectors.

2.1.4 Configuring a Vector

The Deployment Planning dialog contains all parameters required to specify the operation of the instrument. The Deployment Planning frame on the right hand of the dialog displays performance parameters that are automatically updated as you change the parameter settings.
The deployment Planning dialog allows you to specify the instrument operation at two levels. Use the Standard tab to configure the system with default settings for various environments and mounting arrangements. Use the Advanced tab to fine tune the operation parameters. It is recommended to use the Help file that is available within the instrument software for a complete overview of each of the setup parameters, what they mean and what effects tuning them has.
For general recommendations for sampling in specific environments, check out these sections:
Things to Consider, Applications and Common Configuration Scenarios.
Sampling Strategies
A general rule when selecting an appropriate sampling strategy is to consider how often you need data and what type of variations you want to resolve.
Using a Velocimeter 27
Continuous sampling: the instrument is actively collecting data at all times until it is stopped. Burst sampling: the instrument will sample rapidly for a set period of time. A general rule to figure out the maximum sampling rate for a certain configuration is to consider what information you want to resolve.
Sampling Rate
When it comes to sampling rate, the general recommendation is that you will need to sample at least twice as fast as the signal of interest in order to unambiguously resolve it (i.e. the Nyquist sampling criteria). You will need to make a few estimates of what time scales and processes are of interest and select a sample rate appropriate for those. For autonomous deployments: You need to balance memory and power limitations also.
For example, when measuring waves, the sampling should be set up such that the wave record is “well sampled.” This generally means the burst is greater than 15 minutes in duration. This can easily be achieved if the instrument is set to 1 Hz and 1024 samples, or 2 Hz and 2048 samples. This provides over 17 minutes of data and both examples are encouraged setups.
Interna l Sa mpling Rate
The higher the velocity data output rate (for example by selecting 64 Hz in the configuration dialog) the less internal averaging is occurring. This is related to the ping rate. Here are some relevant terminology:
Ping rate: How often the instrument transmits pings. Internal Sampling Rate: The internal sampling rate is fixed within each velocimeter according to its acoustic frequency and velocity range. From a data quality perspective, the interesting parameter is the internal sample rate Sampling Rate: Parameter set in the software. It sets the output rate of the data. It also sets the date at which data are recorded internally or to disk.
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Velocity Range
Internal Sampling Rate (all three beams)
0.01 m/s
70 Hz
0.1 m/s
250 Hz
0.3 m/s
250 Hz
1 m/s
125 Hz
2 m/s
125 Hz
4 m/s
125 Hz
7 m/s
125 Hz
For a given velocity range, the internal ping rate is constant and independent of the "sampling rate" used in the software setup and which tells how often the Vector should output data.
Example : If the Vector is configured with a 1 m/s velocity range, it has an internal sampling rate of 125 Hz. Each Vector measurement interval uses all of the available samples. If the Sampling rate is set to 64 Hz, then most of the output records will be averages of 2 samples, but a few will have only one sample (125/64 = 1.95). At 4 Hz, most of the records will hold an average over 31 samples, but about 1/4 will average 32 samples.
Velocity Range
The velocity range is an important parameter to set properly. The range is a nominal value and the exact maximum velocity is different along the vertical axis (i.e., toward the transmitter) and in the horizontal plane.
Example : If the velocity range is set to +/-30 cm/s, the maximum velocity Vz is 30 cm/s toward the transducer and 81 cm/s in the plane perpendicular to the transmit axis (Vx and Vy). The ratio between the software adjustable (nominal) velocity range and the maximum value for Vx, Vy, and Vz does not remain constant but is different for each setting.
As a general rule, the velocity range should always be set as small as possible. If for example, the maximum expected velocity is 8 cm/s, the velocity range should be set to +/- 10 cm/s. The reason for this is that the noise in the data increases with increasing velocity range. If we set the velocity range to +/-70 cm/s and the actual velocity is only 2 cm/s the data will appear excessively noisy.
If the conditions are not known in advance, the velocity range must be set high enough to cover the whole deployment period. Be aware that the velocity range must cover the full range of wave motion on top of the mean current. If, for example, the mean currents are expected to be around 10 cm/s and the wave orbital velocity may reach 40 cm/s, the velocity range should be set to 1 m/s.
Speed of Sound
The instruments use the speed of sound to compute velocity from the measured Doppler shift, so this information is of vital importance. The speed of sound in water is primarily a function of temperature and salinity. The temperature is measured by a thermistor embedded in the probe and reported in degrees Celsius, and this information is used when selecting Measured speed of sound. If the measurements are to be done in an area with changing salinity (for example, an estuary), it can be an idea to use a fixed speed of sound and correnct the measurements for speed of sound errors as a post processing step.

2.1.5 Data Collection

The Vector system allows for both stand-alone (self-recording) and real-time data collection (monitoring applications). Both applications share the same procedure for the deployment planning (i.e. instrument configuration). A typical sequence includes:
1. Test the Vector as described in Initial Preparation.
2. Erase recorder. Click Deployment > Erase Recorder.
3. Set the real time clock in your PC (the correct time of day).
4. Set the pressure offset: On-line > Set Pressure Offset.
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Using a Velocimeter 29
5. Use the Vector software to plan the deployment. Click Deployment > Planning.
6. Install the Vector in its frame, and run a compass calibration. Click On-line > Compass Calibration.
7. Start deployment. Click Deployment > Start Recorder Deployment (Stand-alone) or Start Data Collection (Real-time).
8. Enter a 6-character deployment name.
9. If appropriate, set a delayed start-up time.
10. Disconnect cable and install dummy plug. Insert plug pins with silicone spray.
11. Install on site. Ensure that the acoustic beams point where you want and that they are not obstructed. If you use a cable probe and configure the instrument to measure in ENU, please remember that the probe and the main housing need to be aligned.
Note: If you set the Vector to collect data, remove power, and then re-apply power later, the Vector will immediately resume data collection. Remember that the date and time may be lost if the power is gone for some time.
Although designed primarily for autonomous deployments, the Vector may just as well be used in monitoring applications with online connection to a remote computer. You may then set up the Vector to record a copy of all data acquired to the internal recorder, in addition to have the data transferred to the remote computer. This is called Recorder Data Collection, as opposed to Deployment (see buttons in the Vector software).
The Vector may also be used together with other sensors or with a controller. When used with a controller, the controller may serve as an external storage device (if applicable) and it may provide power and sampling control creating a very sophisticated system. All this is treated in detail in the
Integrators Guide - Classic.

2.1.6 Mounting and Handling the Probe

It is important to remember that any motion of the instrument can significantly alter the flow pattern and amplify the vortex-induced forces. A primary goal is thus to keep the instrument from moving. If not, an IMU should be considered. Self-disturbance of flow can be a source of data contamination for Vectors. Flow disturbance affects your measurements, and significant errors can be generated when the sensor samples in its own turbulent wake. Thus, it is important to consider the effects large objects will have on the flow itself. A rough rule of thumb is that objects disturb the flow as far as 10 diameters away from the object. Flow disturbance is greatest directly downstream in the wake behind the object. Use extra attention to ensure that no part of the deployment comes in the way of the beams (mooring line, buoy, frame, etc.). Objects in the way of the beams will corrupt the data. Objects interfering with the beams may violate your data. When wave measurements are of interest; usually we aim to classify the incident wave and current field, therefore it is critical that we deploy the instrument in a location that exposes it to an incident wave environment that is undisturbed by its surroundings. Some neighboring structures that influence the data collection could include piers, breakwaters, unusual changes in bathymetry, as well as rivers (or exposure to high currents). Such structures affect the local wave field by reflections, diffraction, refraction, evanescent modes, etc. For example, an instrument deployed in front of a breakwater would be exposed to the combined incident and reflected waves. The PUV approach does not have the ability to separate these two fields. Therefore close proximity to any of the above listed is discouraged, unless of course the objective of the data collection exercise is to measure the locally influenced wave environment at the particular location of deployment. Make sure that there is enough return signal from the scatters in the water. The Vector needs a certain signal-to-noise ratio, SNR to get accurate estimates. The more scattering particles there are in the water, the better the SNR. Mounting on or near metal that influences the magnetic field should be avoided. If this cannot be avoided then the user can either calibrate the effects (run the compass calibration), or note the orientation of the instrument in its deployment position (heading) so that it may be corrected during data processing. The data can also be collected in XYZ coordinates instead of relying on
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Figure : XYZ coor dinates re lative to probe head
the magnetometer (compass). By using XYZ coordinates, the data will not be transformed to ENU coordinates, and are thus not in the risk of being incorrectly transformed. The whole deployment system might move into a different measurement site if care is not taken. The shifting tide combined with a slack mooring line might result in a shift in deployment location. It is important to consider stretching of the mooring components under tension, especially the mooring line, in order to know the exact horizontal and vertical position of the instrument. The deployment depth should not exceed the depth limitations of the instrument’s pressure sensor. The absolute maximum pressure the sensor can handle is a pressure twice its range. For example, the standard 50 m pressure sensor can safely withstand 100 m depth, but it will not record meaningful data beyond 50 m. It has only been calibrated to 50 m. Beyond 100 m it will be damaged. Special consideration must be taken when using a Vector with a cable probe (opposed to the fixed stem type). For the cable probe, it is critical that during data collection in ENU coordinates, the “X” receiver arm (marked with red) is aligned with the “X” mark on the Vector housing. This is because the compass and tilt sensor is located in the Vector housing. The internal tilt sensor determines up or down, and ultimately ensures that the correct coordinate system is used for the directional estimates. If you collect data in beam or XYZ coordinates, you can mount the probe in whatever direction you want. Boundaries are not a concern in mid waters, but if you want to use the instrument near the bottom or surface, you should consider the effects of boundaries as you design your experiment. Use the
Distance Check functionality for useful input.
If the batteries need to be replaced or re-changed or the data need to be downloaded on a regular basis, the deployment should facilitate easy recovery and redeployment.

2.1.7 Orientation of Vector probes

The Vector XYZ coordinates are different depending on the orientation of the tilt sensor and if it is cabled or fixed stem probe. The tilt sensor and compass are both located in the housing. The SNR, amplitude and correlation data you have gathered are not dependent on attitude, they are always collected with reference to beam coordinates. In the image below you can see the XYZ coordinates relative to the probe head.
The orientation of the tilt sensor is easy to find out by doing simply bench test and rotating the instrument to see when pitch and roll approaches zero.
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Using a Velocimeter 31
Figure : Orientation of V ector Cable Probe
In a situation where tilt (and therefore heading) values are incorrect due to the instrument and probe not being aligned the XYZ and Beam coordinates are still valid. XYZ and Beam velocity data are gathered with respect to the probe head only.
Special consideration must be taken when using a Vector with a cabled transducer array (opposed to the firmly attached stem type). For the cabled type, it is critical that during deployment the instrument’s array relative to its body (cylinder) is the same as it is with the Vector with the stem. This is because the internal tilt sensor determines up or down, and ultimately ensures that the correct coordinate system is used for the directional estimates.

2.1.8 Measuring Waves

For readers interested in information about wave measurements in general it is recommended to take a look in the Comprehensive Manual - ADCP, as this manual covers this subject in detail. In this manual it is focused on how wave estimates can be retrieved by using a Vector.
Waves on the ocean surface are clear to us all, however less obvious are the subsurface dynamics generated by these waves. Beneath the surface, waves generate an orbital motion as they pass by a point (indicated in the figure below). The motion associated with the waves penetrates down into the water column. Additionally there is also dynamic pressure that is associated with the combined effect of the vertical acceleration and the change with depth of the water column. The ability to measure these dynamics below the surface makes it possible to interpret the waves on the surface and therefore provides the means to estimate many of the wave parameters that are commonly used to describe a sea state, such as height, period, and direction.
The name "PUV" itself is a description of the method as it is an abbreviation of the three quantities measured: Pressure and the two horizontal components of the wave’s orbital velocity, U and V. These measurements are made at the instrument’s deployment depth and because they are co­located at the same point, this is referred to as a “triplet” measurement.
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Figure : De s cription of the or bital velocities beneath a w ave as it
propagates. Note that the orbital velocity atte nuate s w ith de pth.
Orbital Ve locities
When a wave propagates past a point it creates local currents below the surface. These currents are special in the sense that they are changing direction, whereby the crest of a wave will have the affected water below it moving in the direction of propagation, and the affected water below the trough moving in the opposite direction of the propagation, as illustrated in the figure below. This cyclical motion constructs a circular path in the water column and is often referred to as a wave’s orbital velocity. The orbital velocity produced when a wave passes is the basic mechanism for obtaining information about the waves on the surface, by use of linear wave theory. This provides the means to estimate the directional wave parameters that are commonly used to describe the sea state.
An important detail to understand about orbital velocities is that it attenuates exponentially with increased depth and shorter wavelength. The wave energy will only propagate to a certain depth; and the energy cannot be detected below this depth. This means that:
Short waves in deep water do not have an orbital velocity signal that penetrates to the bottom. The depth limit is related the the Wavelength (L), and is typically at depth L/2.
Higher frequency waves attenuate more quickly with depth. Thus there exists a tradeoff between the depth of the measurement location and the ability to measure the higher frequency waves. This is exactly why we are both depth and frequency limited when measuring waves. See example in next section.
Pressure
Another important property when measuring waves is the dynamic pressure. It is largely dependent on the presence of orbital velocities and this means it also experiences attenuation as a function of depth and wavelength. The dynamic pressure is at maximum under the wave crest. The rate of decrease with depth is well understood and modeled by linear wave theory. This allows us to measure the pressure, to rescale the measurement to obtain the wave elevation spectrum at the surface, by use of transfer functions. The pressure data is thus used for the non-directional wave estimates.
2.1.8.1 Processing Method
The instrument samples pressure and measurements of orbital velocities, but the resulting time series of raw measurements is not particularly useful from a practical standpoint. The wave data therefore needs to be processed to yield the relevant wave parameters that can broadly, yet accurately, characterize the sea state.
The PUV analysis provides an accurate estimate of the wave elevation spectra in addition to the direction and the directional spreading. The dynamic pressure measurement provides a means of estimating all the non-directional wave parameters, while the combined P, U, and V measurements allow for estimating the directional wave parameters.
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Using a Velocimeter 33
Acronym
Description
Range
Note
Hm0
Known as Significant Wave Height, defined as the mean of the highest 1/3 of all waves in the record’s ranking.
Meters Tm02
Mean period.
seconds
Tp
Peak period of the waves corresponding to the peak frequency.
seconds
DirTp
Peak direction is the wave direction at the frequency at which a wave energy spectrum reaches its maximum
0-360 degrees
Reported as "From"
SprTp
Measure of the directional variance at peak frequency.
0-360 degrees
Reported as "From"
Mdir
Mean direction. Weighted average of all the directions in the wave spectrum.
0-360 degrees
Reported as "From"
Unidir. Index
Measure of how much of the wave energy over the full spectrum is from a single direction. Value of 1.0 indicates the energy is from one primary direction
Since these estimates are based on the wave energy distribution, and not a direct measure of the free surface, they are considered inferred estimates. Fourier transforms are used to separate the signals into different frequency bands so that it can determine the direction separately for each band. This means that if you have a long-period swell coming from one direction, and a shorter period coming from another, you can tell the direction for each of them separately. The main assumption for standard PUV wave measurements is that waves at a given frequency come from one primary direction.
Limitations
The most important thing to understand about the PUV method is that it is limited to
1. Deployment depths that are shallow (less than 10 meters) and
2. waves that are long (approximately periods of 4 seconds or longer).
The limitation of only measuring long waves (swell) is the one that should raise a warning flag for those who are interested in the complete description of the wave environment.
Example : Investigating a structure’s response only to swell in shallow water. The accuracy of the
solution requires measurements over the entire wind wave band (waves with periods of 0.5-30
seconds). Incomplete coverage of the wind wave band can result in underestimation of wave height
and missing peaks in the spectrum. The only way to improve the coverage of the wind wave band
is to deploy the instrument in relatively shallow water (i.e. 3 meters depth).
2.1.8.2 Wave Pa rameters
The most common non-directional wave parameters describe height and period of the wave field and are single values representative of the time series. In many practical situations, the directions of the waves are also of great interest and these are based on the first pair of Fourier coefficients and describe the mean direction at a given frequency. The Post-processing of raw wave data will lead to classic wave estimates for the following wave parameters:
2.1.8.3 Deployment Conside rations and Cautionary Notes
The PUV approach is based on linear wave theory; occasionally situations arise where linear theory is no longer valid and second order effects become increasingly significant. Such situations occur when one attempts to improve the instrument’s response by placing it in increasingly shallower water. Long waves in shallow water become solitary, and hence have a nonlinear profile that is not accounted for by the PUV transformation. The result is that waves are properly sensed but the wave height is slightly underestimated.
Perhaps the most difficult aspect of classifying sea state via spectral based estimation is the realization of wave energy at high frequencies. These types of spectra prove to be quite tricky. Amongst the problems are the errors in the calculation of moments and cutting off peaks at higher frequency. One scenario is that an instrument placed in 15 meters of water may never detect the energy up above 0.25 Hz.
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Usually, the aim is to classify the incident wave field and therefore it is critical that the instrument is deployed in a location that exposes it to an incident wave environment that is undisturbed by its surroundings. Some neighboring structures that influence the incident waves could include piers, breakwaters, unusual changes in bathymetry, as well as rivers (or exposure to high currents). Such structures affect the local wave field (reflections, diffraction, refraction, evanescent modes, etc.) and are not the best representation of the incident wave field. For example an instrument deployed in front of a breakwater would be exposed to the combined incident and reflected waves. The PUV approach does not have the ability to separate these two fields. Therefore close proximity to any of the above listed is discouraged, unless of course the object of the data collection exercise is to measure the locally influenced wave environment at the particular location of deployment.
For tips on how to configure the Vector for wave measurements, check out the "Setting up for
operation" chapter.
2.1.8.4 Corrections, Me asurement Errors and Uncertainties
Corrections
In case of strong background currents, the measured waves may be affected by a Doppler shift. That is, when currents are directed against the waves, the waves are compressed. When the currents travel in the same direction, the waves are elongated. The resulting spectra will see the peak energy shift slightly to lower or higher frequencies. It is not just the magnitude of the currents that is essential but also the direction. Currents flowing in a direction perpendicular to the wave direction will have no effect on the waves.
The degree to which the Doppler shift modifies the surface waves depends on the current speed relative to the wave propagation speed. This means that slow propagating (short period) waves are the most affected by currents. Measurements that infer the surface waves from either orbital velocity or pressure measurements, like PUV, require special attention regarding background currents. This is because the transfer function used for inferring the surface waves is wavenumber dependent, and it is the wavenumber that is modified by the background currents. The wavenumber solution must take into account the mean current and direction relative to the wave direction.
Measureme nt Errors
Measurements are estimates of the the value of something real. Given a real wave direction, each measurement is an estimate of this direction. If the instrument happens to be measure waves with infintely-long, parallel crests, wave direction is easy to define; it is perpendicular to the wave fronts. However, real waves are rarely so simple. At any given time, wave spreading blurs the wave direction, making the real wave direction meaningful only as an average.
Uncertainty
There are three primary factors in the uncertainty:
1. The actual directional spread of the waves themselves. Uncertainty in the mean wave direction is
proportional to the spreading of the waves.
2. SNR or signal/noise ratio. A noisy measurement increases the apparent spreading and the
uncertainty of the measurement.
3. Averaging. Like most estimators, averaging produces more accurate estimates.
The directional estimator is unbiased, so averaging should always reduce the uncertainty. In contrast, the spreading estimator is biased. Averaging still helps, but you will always have a residual bias, the magnitude of which depends on the amount of spreading.
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2.1.9 Optional IMU

Figure : The IMU s e nsor re places the com pas s board
Figure : Location of IMU relative to ste m
Nortek offers the Vector with an optional integrated Intertial Motion Unit (IMU). This sensor is intended to help understand how the Vector's own motion influences the measurements. The simple configuration allows one to record motion data simultaneously with the Vector velocity data. The data from the IMU sensor are sampled and stored in realtime, so the velocity measurements and the motion and orientation measurements are tightly synchronized. Before continuing; be aware that the description below applies for Vectors using firmware/software versions from V3.42/V1.39 and onward. If you use older versions, an update is recommended.
Physically, the IMU is incorporated in the Vector by simply using the magnetometer contact interface. This means the standard tilt and magnetometer are removed and replaced with the IMU. So there is no standard Nortek compass system with the IMU integrated.
Note that the use of IMU demands the use of 4GB recorder, due to the amount of data collected.
Using a Velocimeter 35
The velocity measurements and the IMU data will be presented in the coordinate system selected. The IMU can be used as an AHRS; since the Vector with IMU can be used in any orientation (horizontally, vertically,..) while simultaneously converting the measured velocities to ENU, - thus a full 3D solution. We also indicate the heading, pitch and roll to the direction the instrument had during the measuring period.
Note that there is no advanced internal processing as this is left with the end user. The software does only correct for orientation, it does not manipulate velocity other than transforming it to ENU. Correcting for movement will have to be done as a next processing step by the user, using e.g. delta velocity/delta angle. But the good news is that the orientation will be correct even when there is movement.
The end user would benefit by understanding the sensor itself. This may be done by visiting the product page and looking at the Documentation tab: http://www.microstrain.com/inertial/3DM-GX3-
25-OEM
The location of of the IMU is relevant if e.g. removing the affect of mooring vibrations are of interest. The center of the sensor is 16 cm from the end of the endbell where the probe stem is affixed.
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2.1.10 Data handling

Data
The Vector creates binary files (*.vec), which can be converted to ASCII format files by using the Data Conversion tool within the Vector software. The Vector records the following:
The *.hdr file is a self-documented table. Please note that this file contains the detailed data
format of all the other ASCII files.
The *.dat files contains velocity and pressure data at the full sample rate.
The *.sen files contains system data such as the time/date, compass, tilt, temperature, battery
voltage, etc. These data are sampled once per second
The *.pck contains the probe check data
The *.vhd contains the Velocity header data - the data that is collected during the very first second
when running Continuous mode, or at the start and end of each Burst.
The ASCII files are easy to import into most spreadsheets and data analysis programs.
Check out our web pages to gain access to the latest technical notes and user-experience regarding data analysis and related matters.
Quality Assurance and Quality Control Tips:
Check the Looking at Velocimeter Data section. If the data looks different from what you expected and you have reason to believe that this is instrument or deployment related, consult the Troubleshooting section before spending too much time on QA/QC.
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2.2 Vectrino

Using a Velocimeter 37

2.2.1 Technical description

For technical specifications, check out the product on our website.
Probe
The standard and the field probe is made of stainless steel and consists of four receive transducers and a transmit transducer. It is mounted either on a fixed stem connected to the main housing through the probe endbell, or on a cable connected to the main housing through the same probe endbell.
Transducers
Each of the four receive transducers is mounted inside a receiver arm. The transmit transducer is in the center of the probe.
Electronic Module
The electronic module is located inside the pressure case and consists of a single board with the power transmitter, analog and digital signal processing, power conditioning and interface circuits.
Temperature sensor
The temperature sensor (thermistor) is located inside the probe head
Power and Communication Cable
The power and communication cable is connected to the endbell connector. The cable supplies external DC power (12–48 V) and provides two-way serial communication with an external computer. It also provides four analog outputs (0-5 V DC) for input to an AD converter. The cable also provides synchronization options when the Vectrino is used as master or slave to synchronize measurements with other Vectrinos and/or other instruments.
The Vectrino is shipped with a 12-pin cable and waterproof connector. The Vectrino power lines are diode protected, hence, you do not have to worry about wiring the Vectrino power backwards. If you do, it will not damage your instrument. The pinout is shown in the Service Manual.
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Options
The Vectrino can be shipped with the following components to suit different requirements:
Standard or Vectrino Plus firmware. Upgrading to Vectrino Plus is also available as retrofit
4-beam down-looking probe or side-looking probe. Fixed stem or flexible cable. Changing the
probe is available as retrofit.
Field probe

2.2.2 Instrument software

The Vectrino software is designed to aid in the planning and execution of on-line data collection, and is available in two versions:
Vectrino, 25 Hz sampling
Vectrino Plus, 200 Hz sampling
The Vectrino Plus software is used with Vectrinos with the Plus firmware installed, and provides a wider range for some of the settings than the standard version does. It is emphasized that the Vectrino and Vectrino Plus software is not primarily designed for controlling multiple instruments. For these types of measurements, we instead recommend using Polysync.
The Vectrino and/or the Vectrino Plus software can be found on the flash disk that came with the instrument, or on the Nortek web site: www.nortekgroup.com/software. Nortek Windows programs run on all versions since XP (SP3), including Windows 8.
Installing the PC Software
Follow these steps to install the software on a computer running Windows:
1. Insert the Flash disk
2. Follow the on-screen instructions. Accept the default settings. The Setup program will by default
install the application in the c:\Nortek\Vectrino folder and create an application shortcut in the Nortek programs folder and on the desktop.
3. Restart your PC if prompted to, to finalize the installation process.
Software Help
An on-line help is integrated in the software, and it contains answers to all questions you may have on how to use the software. Click Help > Help Topics.

2.2.3 Initia l preparation

Communication
Check that you have installed the software correctly according to the procedure in the previous section, and then follow this procedure to test the communication:
1. Using the enclosed cable, plug in the AC adapter, and connect the Vectrino cable and the Serial-
to-USB converter to the USB port on your computer.
2. Start the Vectrino software.
3. Select Communication > Serial Port, and specify which port number to use.
4. Accept the default baud rate settings (19200 baud), which is also the default baud rate for the
instrument.
5. Click the Connect toolbar button. The Vectrino instrument should reply with an identification
string.
Baud ra tes
The baud rate is specified in the Serial Port dialog box. There are two baud rates that can be specified; one for normal communication and data transfer, and one for firmware upgrades. For the standard Vectrino, the default baud rate is19200. For the Vectrino Plus, the default is 57600.
The baud rate settings for transfer of head files and firmware upgrades may differ from those for transmission of deployment setups and for online data collection. The reason is that the former
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Using a Velocimeter 39
Baud Rate
Max Sampling Rate
300
1 Hz
600
2 Hz
1200
4 Hz
2400
8 Hz
4800
16 Hz
9600
32 Hz
19200
64 Hz
38400
128 Hz
57600
200 Hz
assumes that high transmission rates can be used without problems, i.e. that the cable connecting the computer to the instrument is short. A higher baud rate may reduce the download time, but note that the baud rate is limited to the operating system of the PC, the serial port, and the length of the USB cable. If you experience communication issues after changing the baud rate, try changing it back to the default.
The baud rate setting can be changed if you upgrade in-situ using long cables. The Vectrino verifies the received head file and firmware upgrade files before they are allowed to replace the existing head and firmware files, hence, using the wrong transmission speed will not cause trouble.
The table below shows the highest permissible sampling rate for a given baud rate (Vectrino).
Check the transducers
1. Fill a bucket with water and a little sound-scattering material ("Seeding").
2. Click Data collection > Start Data Collection. While the transducers are in the air, the velocity
measurement will look like random noise.
3. Immerse the transducers in the water, and observe the velocity, the standard deviation, and the
amplitude in counts. Note the change in the graphical view of the velocity when the probe is lowered into the water. In the air the graphs are noisy; in water they should be smooth. Noisy velocity graphs: If the velocity graphs remain noisy when the probe is immersed in water, try varying the position of the probe, or add some seeding like dirt or small particles to the water.
4. Designed to act as a measurement quality assurance tool, the Probe Check function in the
Vectrino software lets you inspect the region where the Vectrino makes its measurements by showing how the signal varies with range. You can use it to diagnose and correct problems and to optimize data collection. Click Data Collection > Probe Check to start the Probe Check.

2.2.4 Configuring a Vectrino

The Deployment Planning dialog contains all parameters required to specify the operation of the instrument. The Deployment planning frame on the right hand of the dialog displays performance parameters that are automatically updated as you change the parameter settings. It is recommended to use the Help file that is available within the instrument software for a complete description for each of the setup parameters available.
For general recommendations for sampling in specific environments, check out these sections:
Things to Consider, Applications and Common Configuration Scenarios.
Sampling rate
When it comes to sampling rate, the general recommendation is that you will need to sample at least twice as fast as your signal of interest in order to unambiguously resolve it (i.e. the Nyquist sampling criteria). You will need to make a few estimates of what time scales and processes are of interest and select a sample rate appropriate for those.
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Nominal Velocity Range
The velocity range is set before data collection is started. The range is a nominal value and the exact maximum velocity is different along the vertical axis (i.e., toward the transmitter) and in the horizontal plane. The horizontal and vertical ranges are presented in the planning dialog. Setting the velocity range to an appropriate value for the flow being measured is the most important instrument parameter in order to get good data quality. Too large a velocity range will result in noisy data because the detected phase shift is very small relative to the ambiguity velocity. Too low a range will result in de-correlation of the return signals or phase wrapping. The appropriate Nominal Velocity Range will generate good quality data minimizing data quality problems.
For example, if the velocity range is set to +/-0.3 m/s, the maximum velocity Vz is 0.27 m/s
toward the transducer and 0.94 m/s in the plane perpendicular to the transmit axis (Vx and Vy).
The ratio between the software adjustable (nominal) velocity range and the maximum value for Vx,
Vy, and Vz does not remain constant but is different for each range setting.
As a general rule, the velocity range should always be set as small as possible, but still cover the expected velocities.
For example, if the maximum expected velocity is 4 cm/s, the velocity range should be set to +/-
0.1 m/s. The reason for this is that the noise in the data increases with increasing velocity range. If
we set the velocity range to +/- 4 m/s and the actual velocity is only 2 cm/s the data will appear
excessively noisy.
If the conditions are not known in advance, the velocity range must be set high enough to cover the whole deployment period. Be aware that the velocity range must cover the full range of wave motion on top of the mean current. If, for example, the mean currents are expected to be around 0.1 m/s and the wave orbital velocity may reach 0.4 m/s, the velocity range should be set to 1 m/s.
Adjusting sampling volume and/or transmit le ngth
Transmit length is the length of the acoustic pulses transmitted by the instrument. In theory, sample volume size is entirely independent and set by the amount of time spent listening. In reality, the sampling volume size has been optimized for a given transmit length for the best performance.
Theoretically, a shorter transmit length is better because it results in a higher signal bandwidth. In reality, the SNR will decrease simply because there is less energy in the return signal. There are tradeoffs to be made, but usually there is not a need to change the transmit length to try and further optimizes performance. The exception is if the user is trying to get closer to boundaries.
Power Level
There are four different power levels:
Low-
Low+
High-
and High+.
It is about 6dB difference in SNR between High+ and High -, 10 dB between High- and Low + and about 6dB between Low + and Low -. Adjusting the power level should thus be related to the signal strength, so if the scattering level is low then the power level should be set to High.
Take a look at the Probe Check section for a couple of examples on how to determine whether the power level should be increased or decreased from the default setting.
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2.2.5 Mounting and Handling the Probe

When using an instrument in a laboratory flume, it is recommended to ensure alignment of the coordinate system. For a quick setup, aligning everything by eye works surprisingly well if you have good references to align against (e.g. flume walls). For a more rigorous setup, two spirit levels mounted orthogonal to one another can be used to make sure the mounting fixture and probe are level. This assumes the top of your flume is level since everything is usually mounted on a cross piece to it.
Follow these guidelines when you mount your Vectrino:
Make sure that there are no obstructions between the sensor and the focal point (sampling
volume) located about 5 cm from the transducers for the standard Vectrino, 10 cm for the field
probe.
When mounting the sensor, use the recessions to strap it to the structure. Never use the probe
stem as mounting point.
Consider the effects of large objects on the flow itself. A rough rule of thumb is that objects disturb
the flow as far as 10 diameters away from the object. Flow disturbance is greatest directly
downstream in the wake behind the object.
All acoustic transducers must be submerged during data collection. Operating your instrument
when the transducers are out of water will not cause any damage, but your data will be
meaningless. For side-looking probes, it is possible to collect 2D-data with only the lower receiver
arms submerged.
The best quality is achieved if the main flow direction is perpendicular to the transmit axis. Flow
directly into the transmit axis should be avoided.
Make sure your mounting structure is stable. Small vibrations in the mount can generate large
accelerations in the data.
After mounting the instrument, run a Probe Check as a diagnostic tool to confirm that the
sampling volume and signal strength looks good.
Using a Velocimeter 41
If the flow is dominantly 1D, the side-mounted configuration where the transmitter is orientated perpendicular to flow direction is preferable. There are two main reasons for this:
It avoids any possible flow interference from the probe into the sampling volume (especially
relevant for wave measurements)
It avoids bottom interference through the weak spot problem.
When two probes are close together, there is a chance of acoustic cross interference. Mostly, this should happen when one unit is transmitting and the other is receiving. For this reason, it is probably wise that the two probes are not mechanically coupled. Otherwise, the cross interference is going to be a function of the particle concentration - lots of particles give strong return signal and the effect of the cross interference will be less important. Please be aware that the transmitters in the two systems are asynchronous - even if the data collection is synchronized using the synch input/output lines. This also means that a test to check for cross interference should be left to run for at least 5 minutes. Note that for the Vectrino Plus version, the firmware allows for synchronization of the transmit pulses.

2.2.6 Data Handling

Data
The Vectrino software saves data in binary files (*.vno), which are easily converted to ASCII format files, using the conversion module in the software.
The *.hdr file is a self-documented table. Please note that this file contains a detailed data format
description of all files that are generated.
The *.dat file contains velocity data at the full sample rate.
The *.pck contains the probe check data
ASCII files are easily imported into most spreadsheets and data analysis programs.
QA/QC
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Check the Looking at Velocimeter Data section.
Typical processing tasks:
1. Assess data quality (QA/QC)
2. Data screening
3. Statistics to describe the flow (mean, variance)
4. Spectral Analysis (turbulence, waves)
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2.3 Vectrino Profiler

Using a Velocimeter 43

2.3.1 Technical description

For technical specifications, check out the product on our website.
Probe
The probe is made of stainless steel and consists of four receive transducers and a transmit transducer. It is mounted either on a fixed stem connected to the main housing through the probe endbell, or on a cable connected to the main housing through the same probe endbell.
Transducers
Each of the four receive transducers is mounted inside a receiver arm. The transmit transducer is in the center of the probe.
Electronics Modules
The electronics module is located inside the pressure case and consists of a single board with the power transmitter, analog and digital signal processing, power conditioning and interface circuits.
Temperature sensor
The temperature sensor (thermistor) is located inside the probe head.
Power and Communication Cable
The power and communication cable is connected to the endbell connector. The cable supplies external DC power (12-48V) and provides two-way serial communication with external computer.
The cable also provides synchronization options when the Vectrino Profiler is used as master or slave to synchronize measurements with other Vectrino Profiler's and/or other instruments.
Cable wiring: The Vectrino Profiler is shipped with a 12-pin connector and communication cable. The connector type is an MCBH-12-FS waterproof connector. The pin out and wiring of the cable can be found in the Wiring of Cable chapter.
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The Vectrino Profiler power lines are diode protected, hence, you do not have to worry about wiring the power backwards. If you do, it will not damage your instrument.
USB-Serial Converter
The USB-Serial converter is a high-speed device which supports up to a 1.25 MBaud transmission rate over shorter distances. It is important that the most up to date version of the drivers be installed with the converter. Driver updates are available from the FTDI web site at http://www.ftdichip.com/
Drivers/VCP.htm.
At high sampling rates (above 60 Hz), the driver parameters need to be tuned to provide an adequate display rate for the application software. Without this tuning, higher sampling rates will appear to be slow and bursty.
Open Windows Device Manager, expand Ports (Com and LPT), right-click on the appropriate serial
port and select Properties.
With the properties in view, click on the Port Settings tab. The baud rate displayed (9600 in the
menu shown) doesn’t have to be changed. The application will automatically set the baud rate of
both the USB-serial port and the instrument to the requested rate in the connection menu so this
driver entry can be left unchanged.
Click on the Advanced button
Change the Latency Timer to 5 msec. Faster systems should be able to use 2 msec.
Remove and re-insert the USB connector to activate the parameters.
While having a lower latency timer is better, it can result in significantly higher CPU usage on slower machines. If the data transfer from the instrument has degraded noticeably with the new latency timer, increase it to a larger number. Ideally, this number should not be larger than 8 ms or the data display refresh will start becoming choppy at higher sampling rates. The software will warn the user if it detects that the latency timer has not been correctly set.

2.3.2 Instrument software

Find the software on the memory stick that came with the instrument, or on the web site. To install the software, double-click on Vectrino Profiler_setup.exe. This will copy the appropriate files to the installation directory and create a shortcut to the application on the desktop.
The Vectrino Profiler acquisition software on the included memory stick requires Java virtual machine (JVM) to operated. The software has been tested with the sun JVM available from http://www.java.
com/ but is also known to be fully functional with other JVMs.
Double clicking on the software shortcut will start it. The application initially displays an empty instrument panel. To connect to an instrument, select Communication: Connect and choose the desired instrument. This will bring up a connection dialog box for the instrument. Then:
Select the appropriate serial port and port speed (baud rate) and press Apply.
A baud rate of 937500 is recommended for best performance of the Vectrino Profiler
An instrument name can be specified if desired. This will help to differentiate between instruments
when several are used in the same experiment.
Setting the serial port to SIM will simulate an instrument connected to the serial port.
After the instrument has been connected, an instrument display panel is created showing the associated data displays for the current configuration as well as the action buttons for the instrument. In addition to the action buttons, a status display is shown on the upper right of the panel. This shows the instrument name and type and four status lights used to display status information while collecting data (run status, collection status, connection status, and instrument status). Hovering the mouse over each status light will display more detailed information.
For more detailed information using the software, check the SW User Guide, available under "Help".
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2.3.3 Initia l preparation

Communication
Check that you have installed the software correctly according to the procedure in the previous chapter, Instrument Software, and then follow this procedure to test the communication:
1. Using the enclosed cables, plug in the AC adapter, and connect the Vectrino Profiler cable and
USB converter to the USB port on your computer.
2. Start the Vectrino Profiler software.
3. Select Connect:Vectrino Profiler, and specify which port number to use, and communication
speed
4. Click on Apply to initiate communication with the instrument
Check the transducers
1. Fill a bucket with water and a little sound-scattering material.
2. Click the Start Collecting Data button. While the transducers are in the air, the velocity
measurement will look like random noise.
3. Immerse the transducers in the water, and observe the velocity, the standard deviation, and the
amplitude in counts. Note the change in the graphical view of the velocity when the probe is lowered into the water. In the air the graphs are noisy; in water they should be smooth. Noisy velocity graphs: If the velocity graphs remain noisy when the probe is immersed in water, try varying the position of the probe, or add some seeding like dirt or small particles to the water.
4. Designed to act as a measurement quality assurance tool, the Probe Check function in the
software lets you inspect the region where the sensor makes its measurements by showing how the signal varies with range. You can use it to diagnose and correct problems and to optimize data collection.
Using a Velocimeter 45

2.3.4 Configuring a Vectrino Profiler

The Doppler tab in the software is used when configuring the velocity profiling parameters.
The Sampling rate determines how often velocity records are collected. Individual velocity samples are collected at a rate related to the ping interval (related to the velocity range) and averaged over the sampling rate period to produce a final velocity estimate. The Data rate bar shows the transmit bandwidth being consumed for the given configuration. If the bandwidth exceeds that of the serial port speed, the data will be buffered internally within the instrument before being transferred to the host computer.
The Velocity range, combined with the Ping algorithm determines the appropriate ping timing parameters to achieve the desired velocity. The Extended Velocity Active field indicates whether or not the selected velocity range corresponds to dual PRF operation.
Three algorithm choices are available for the ping algorithm:
Max interval: Produces the longest possible ping interval to achieve desired ambiguity velocity and
sampling range. This is best used for smooth flow conditions.
Min interval: Produces the smallest possible ping interval to achieve the sampling range and, at
minimum, the desired ambiguity velocity. This is best used for turbulent measurements
Adaptive: Collects a long profile and examines the return echoes to determine where acoustic
interference is occurring. The ping rate is then calculated to achieve the desired ambiguity velocity
and sampling range while minimizing / removing acoustic interference. The adaptive ping interval
selection is carried out with every configuration performed so the ping intervals selected may vary
when the beam return signals change. This is the best general choice. The adaptive check allows
the ping intervals to be adjusted dynamically during data collection to account for changing
conditions within the environment. Options range from Once (perform adaptive check only during
the configuration phase at the start of acquisition; static checking) to 1/sec (dynamic checking).
The corresponding horizontal and vertical ambiguity velocities are displayed (assuming the probe is facing down). The vertical ambiguity velocity corresponds quite closely to the beam velocity.
For point measurement instruments, the measured region starts at Range to first cell mm and is of
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length Cell size mm. For profiling instruments, the measured region starts at Range to first cell mm from the transducer and ends at Range to last cell mm from the transducer with each cell being Cell size mm in length.
The Power level setting is used to adjust the amount of power supplied to the active transducer during transmit. Under normal situations, using a setting of High is appropriate since this will provide the highest signal to noise ratio.
For general recommendations for sampling in specific environments, check out these sections:
Things to Consider, Applications and Common Configuration Scenarios.

2.3.5 Mounting and Handling the Probe

When using an instrument in a laboratory flume, it is recommended to ensure alignment of the coordinate system. For a quick setup, aligning everything by eye works surprisingly well if you have good references to align against (e.g. flume walls). For a more rigorous setup, two spirit levels mounted orthogonal to one another can be used to make sure the mounting fixture and probe are level. This assumes the top of your flume is level since everything is usually mounted on a cross piece to it.
Follow these guidelines when you mount your Vectrino Profiler:
Make sure that there are no obstructions between the sensor and the focal point (sampling
volume) located about 5 cm from the transducers.
When mounting your sensor, use the recessions to strap it to the structure. Never use the probe
stem as mounting point.
Consider the effects of large objects on the flow itself. A rough rule of thumb is that objects disturb
the flow as far as 10 diameters away from the object. Flow disturbance is greatest directly
downstream in the wake behind the object.
All acoustic transducers must be submerged during data collection. Operating your Vectrino
Profiler when the transducers are out of water will not cause any damage, but your data will be
meaningless. For side-looking probes, it is possible to collect 2D-data with only the lower receiver
arms submerged.
The best quality is achieved if the main flow direction is perpendicular to the transmit axis. Flow
directly into the transmit axis should be avoided.
Make sure your mounting structure is stable. Small vibrations in the mount can generate large
accelerations in the data.
After mounting the Vectrino Profiler, run a Probe Check as a diagnostic tool to ensure that the
sampling volume and signal strength looks good.
When two probes are close together, there is a chance of acoustic cross interference. Mostly, this should happen when one unit is transmitting and the other is receiving. For this reason, it is probably wise that the two probes are not mechanically coupled. Otherwise, the cross interference is going to be a function of the particle concentration - lots of particles give strong return signal and the effect of the cross interference will be less important. Please be aware that the transmitters in the two systems are asynchronous - even if the data collection is synchronized using the synch input/output lines. This also means that a test to check for cross interference should be left to run for at least 5 minutes.

2.3.6 Data Handling

The Vectrino Profiler software saves data in binary files (.ntk), which are easily converted to Matlab structured arrays or ASCII format files, using the conversion module in the software.
Matlab: The .mat file contains Data and Config structured arrays. Each array contains a "Comments" and "Units" field that describe the contents of each structure.
ASCII:
The .hdr file is a self-documented table
The .dat file contains velocity data at the full sample rate
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ASCII files are easily imported into most spreadsheets and data analysis programs
QA/QC
Check the Looking at Velocimeter Data section.
Typical processing tasks:
1. Assess data quality (QA/QC)
2. Data screening
3. Statistics to describe the flow (mean, variance)
4. Spectral Analysis (turbulence, waves)

2.4 Things to Consider

This section contains an collection of things to be aware of when using a Velocimeter.

2.4.1 Probe Check

The Probe Check is a powerful tool to give insight into the operation of the instrument. This tool produces long average amplitude vs. range profiles for each beam when data collection is started, and thus gives you "eyes" onto the region where the instrument is making measurements by showing how the signal varies with range.
Using a Velocimeter 47
Vector: The probe check data is available in two ways: Before and after each burst a probe check is made, or at the beginning of the measurement when selecting Continuous mode. Continuous probe check can be gathered if the recording to disk function is enabled before starting a probe check in the Vector software (Online > Start Probe Check)
After a binary to ASCII conversion it ends up in the .pck file as explained in the .hdr file. ExploreV does not handle the probe check data so you will need to use another program like Matlab to plot this data. Note that when recording to disk, the data will be in binary mode. The format is described in the System Integrator Manual.
Vectrino and Vectrino+: Click Data Collection > Start Probe Check. When exporting data using the "Data Conversion" function the data will be automatically produced if it is available. Look in the directory where the data file is located, and after conversion you will see a few additional files created. The instrument configuration information and other (data) file formats are found in the *.hdr file. The probe check data (if it is contained in the data file) will be in a file with the suffix *.pck. ExploreV does not handle the probe check data so you will need to use another program like Matlab to plot this data.
Vectrino Profiler: The Probe Check must be enabled in the Configuration Dialog. The probe check data can be found in the "Data" structure when converting the data to Matlab format (ProbeCheckBeam*).
The probe check output in the first figure below is from a Vectrino, but a similar output is expected from the Vector and Vectrino+. Note the amplitude at the beginning of the sampling volume (A), the nice gaussian peak that indicates the sampling volume (B) and the peak corresponding to the bottom (C). Also note that the signal strength decrease to the noise floor between the measurement volume and the bottom, and that all colored graphs show roughly the same amplitude and profile shape. The four graphs correspond to each of the four receive beams. Graphs are scaled in distance in mm from the transmit transducer, parallel to the transmit beam. This is also relevant for the side­looking probe. The peak in beam 2 should reach over 100-150 counts. For the Vector, the sampling volume is located at 150 cm from the probe, not 5 cm as for the Vectrino (10 cm for the field version)
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Ve ctor and Vectrino: Note the am plitude at the be ginning of the sampling volum e (A), the nice gaussian
peak that indicates the s am pling volume (B) and the peak cor r esponding to the bottom (C). Also note that
the s ignal stre ngth decre as e to the noise floor be tw e e n the m e asurem e nt volum e and the bottom , and
that all color e d graphs show roughly the same am plitude and profile shape .
Ve ctr ino Profiler: Note that the s ignal strength is presente d in dB and not counts . As above , you s hould
se e a br oad peak cente red around ~5 cm the profiling volum e . Each color e d gr aph corre s pond to the
each of the four beam s. No bottom r e turn are vis ible in this case .
The probe check output in the figure below is from the Vectrino Profiler. The four colored graphs in the profile display correspond to each of the four receive beams. The broad peal centered at 5 cm is the valid profiling volume.
If the results of a probe check differs from the above figures, it is recommended to take a look at out
Troubleshooting Guide for some examples.
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2.4.2 Distance Check

Bottom check processing determines the distance from the center transducer to the bottom at a given sampling rate (up to 10 Hz). Bottom check data collection can be either enabled or disabled. When enabled, velocity profiling is paused for a short period of time (~4ms) while the bottom check calculation is made. The subsequent velocity sample taken is averaged for a correspondingly shorter period of time to accommodate for the bottom check while maintaining the same velocity sampling rate. This shortened period is reflected in the AveragedPingPairs field associated with the velocity record in the data and displayed in the text output pane.
For the interested reader: The bottom check sample rate used during data collection will be somewhat different from that selected. Given that the bottom check and velocity sample rates are interleaved, the actual bottom check sample interval will be an integral multiple of the velocity sample interval. For example, if the velocity sample rate is 60 Hz (~16.7 ms) and the bottom check sample rate is 8 Hz (125.0 ms), then the actual bottom check spacing will be 116 ms (~8.6 Hz).
In order for bottom check to be effective over larger distances, the instrument should be carefully oriented. The central transducer used for bottom check functionality is directional. If the probe is tilted with respect to the bottom surface, then the signal may be reflected away from the transducer, preventing the bottom echo from being visible in the profile data.
Tip for Vectrino Profiler users: When configuring bottom check, having the bottom peak centred in the display window (if the instrument is licensed for profiling bottom checks) with a reasonable number of low intensity points on either side is optimal. The bottom check process determines a peak level and curve fits a quadratic to the surrounding points. The vertex of this quadratic is used when determining the measured distance to bottom.
Using a Velocimeter 49

2.4.3 Velocity Ambiguity and Phase Wrap

An inherent problem with coherent Doppler processing for Velocimeters is the potential of velocity ambiguity. This arises as a result of the fact that the phase difference can only be determined to
within ±π radians. If the absolute value of is greater than π, phase wrapping occurs and the
measured phase shift has a value . We see this phase wrapping in a velocity trace as an abrupt, unrealistic change in magnitude and almost always with a change in sign. While it is possible for phase wrapping to occur without a sign change, this would be the result
of an extremely large wrap where the phase shift exceeds 2π. The ambiguity velocity can be
estimated:
Here, F_source is the frequency of the transmitted wave and C is the speed of sound in water. The
choice of ∆t is crucial for correct operation of the instrument; the size of the separation between
pulses determines the maximum unambiguous velocity that can be measured. Longer lags have lower maximum velocities, while shorter lags have higher maximum velocities. Conversely, longer lags will typically have lower noise levels than shorter lags. The lags are controlled by the velocity range setting.
The simplest way to avoid phase wrapping is to have a little prior knowledge of flow conditions and to set up the instrument appropriately for the environment. The latter is done in the Deployment Planning, where you can set the Nominal Velocity Range. This is the maximum velocity you expect to measure during the deployment or experiment. Note that since the transmitter and receiver are physically separated, the measured velocity is along the bistatic axis (ref. Velocimeters). By decomposing the velocity along the bistatic axis onto the vertical and horizontal axes you get the corresponding maximum vertical and horizontal velocity ranges. These ranges are presented in the deployment planning dialog (right part).
Measurement uncertainty is roughly proportional to the Nominal Velocity Range – smaller velocity
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Velocity Range (m/s)
Vector (m)
Vectrino (m)
0.01
3.12
0.03
0.38, 0.75
0.10
0.46
0.23, 0.45
0.30
0.20
0.10, 0.23
1.00
0.08, 0.20
0.05, 0.12
ranges give you better measurements regarding uncertainty. An example of the problem with phase wrapping is discussed in “A Practical Primer for Pulse Coherent Instruments”.
If you have collected data that are subject to phase wrapping, there is a solution. Take a look in our
Troubleshooting Guide for the procedure.
For the Vectrino Profiler, the Extended Velocity Range (EVR) may be an option to increase the velocity range.

2.4.4 Extended Velocity Range

Extended Velocity Range (EVR) utilizes an additional pulse pair to create a set of pulses with two different lags and velocity ranges. With this technique, two alternating ping intervals are used to collect a single profile. We use the first lag to get a course estimate of the velocity and then we use the second and larger lag to improve the estimate. The first lag defines the ambiguity range of the setting and the second is the one that is actually reported after we have used the first estimate to determine what ambiguity branch we are on. The actual lags change with the velocity setting. The velocity calculated using this technique is:
= 4 ( 2 - 1)( 2 - 1)
The ambiguity velocity then becomes:
This technique has the advantage of producing an extended velocity measurement for all cells in the profile (unlike the coarse / fine pulse-pairs technique). Signal noise effectively limits the minimum usable time difference. In practice, the gain is limited to a factor of 3-5. Note that EVR does not eliminate the possibility of ambiguity problems if velocities exceed the specified velocity range in the Deployment Planning dialog.

2.4.5 Weak Spots

The Vector, Vectrino and Vectrino Profiler transmits two pings, and as such, they are susceptible to pulse interference when measuring near boundaries. This especially applies to Vectrino Profiler, as this is a profiling instrument and the pulse is in the measurement volume for a longer period of time. Pulse interference for acoustic Velocimeters is called a “weak spot” and will show in data as low SNR (Signal-to-Noise Ratio) and correlation values, as well as noisy velocity traces.
The table below summarizes the distances where weak spots occur for the Vector and Vectrino indexed to the Nominal Velocity Range setting. Changing to the next higher or lower velocity range as appropriate will eliminate the problem. Alternatively, moving the instrument (measurement volume) up or down away from the boundary by just a few centimeters can reduce the weak spot effects. Note that the distances to boundaries specified are approximate and will depend on the speed of sound and the boundary surface.
= 4 ( 2 - 1)
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Using a Velocimeter 51
2.00
0.05, 0.09
2.50
0.03, 0.10
4.00
0.03, 0.06
0.02, 0.05
7.00
0.02, 0.04
Figure : X, Y, Z1 and Z2 velocity plots. The upper plot s how s X velocity, w hich is subje ct to inte r fe r e nce
due to a w eak spot
Table: Weak s pots lis te d as the dis tance from Sample Volum e to boundar y for the Ve ctor and Vectrino. Note that the w eak s pot location is de pe ndent on the speed of s ound and the boundary surface, s o the values given are only es tim ate s and w eak s pots m ay be e ncountere d a centim e te r or m ore aw ay from the s e values.
The Velocity range specifies the separation in time for the two pulses. This parameter can be adjusted in the Configuration dialog. The rule of thumb is to set the velocity range as low as possible without the potential for water velocities to exceed the horizontal or vertical velocity ranges.
A weak spots is related to the spatial separation between the pulse pairs transmitted by the Velocimeter. A weak spot occurs when the first pulse hits the bottom and the reflected signal of the first pulse reaches the sampling volume at the same time as the second pulse goes through the sampling volume. The two pulses passing through the same volume at the same time creates interference, reducing data quality and generally leading to unusable data. The figure below shows how a weak spot may show up in the data.
The vertical extent of the weak spots is a function of the bottom composition. If the bottom is well defined (e.g. sand) the extent is no bigger than the transmit pulse or about 1 cm. If the bottom is rough, the vertical extent can be larger. It is also a matter of the relative strength between the water
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scattering and the bottom echo - if the water scattering is high the whole issue goes away.
The Vectrino Profiler can make use of adaptive ping intervals to reduce weak spot interference. This allows the ping intervals to be adjusted dynamically during data collection to account for changing conditions within the environment. Options range from Once (perform adaptive check only during the configuration phase at the start of acquisition) or 1/sec (dynamic checking). Using the Max Interval algorithm (also accessible in the Configuration dialog) allows the time interval to be adjusted manually. After setting the velocity range as low as possible, the range can be adjusted to a slightly higher range, to move the weak spots out of the sampling window.

2.4.6 Interference from Highly Refle ctive Bottoms

The bottom material used in a lab environment can have a marked effect on the quality of the data. Surfaces which are acoustically highly reflective will cause very large return signals which pollute the water column in such a way that obtaining reliable data is not possible. We have seen metal bottomed flumes that have very large returns from the bottom; so large, in fact, that they caused large areas of interference in profiles that were stepped up from the bottom.
You can tell how large the return is by looking at the signal return from the bottom check. If the instrument is to be used in such an environment (e.g. a metal bottomed flume), some sort of absorptive material should be placed along the bottom underneath the probe. Thick plexi-glass, a thin layer of acrylic or rubber layer or a concrete block have both been shown to work quite well in removing the bottom reflection interference by providing some acoustic dampening to the return.

2.4.7 Mooring Vibrations

High frequency mooring vibrations due to vortex shedding are caused by current flow past a mooring structure, such as surface and subsurface buoys, mooring lines, risers etc. Alternating vortex shedding produces pressure fluctuations with a dominant component in the direction across the flow direction. The mooring structures, if not mounted rigidly, are very sensitive to excitation from vortex shedding, especially if the frequency of vortex shedding matches the resonance frequency of the structure. This results in resonant vibrations transverse to the flow direction of the ocean currents. The occurrence of vortex induced motion also increases the mean drag force in the current direction, contributing to aggravating the data collection. Increased offset implies increased mooring line tensions.
The part covering vibrations on the mooring is especially important to users of the Vector. This instrument has a high sampling rate, making it especially prone to data contamination due to vibrations. Excessive mooring vibration can adversely affect the data; vibration introduces spurious velocities and interferes with the proper operation of the tilt sensor. The impact of mooring oscillations must be carefully considered. A general solution to improve on data quality is to design a more stable deployment by considering the components that generate mooring vibrations. The addition of aerodynamic devices may partly prevent and partly reduce the strength of vortex induced vibrations.
You may be able to detect intervals of excessive vibration by looking closely at your data. For more accurate measurements of vibration, an accelerometer is the solution. An Integrated Motion Unit
(IMU) is a system that consists of an accelerometer, a gyroscope and a magnetometer that samples
at 10 kHz, and can be integrated with the Nortek Vector. By measuring the acceleration, the tilt and the heading, one can correlate vortex induced vibrations with the sampled current velocities, and during post-processing the measured sensor motions can be removed from the velocity data. Note that the use of IMU demands the use of 4GB recorder, due to the amount of data collected.

2.4.8 Acoustic Streaming (Vectrino and Vectrino Profiler)

The instruments generate acoustic streaming, or secondary flows, as the pulse is transmitted. If ambient flow velocities are of the order of potential acoustic streaming velocities (below 8 cm/s), acoustic streaming may represent a significant source of bias.
This effect can be observed by placing the instrument in still water and observing the flow over a
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period of a few seconds. Induced flows of up to 2-3 cm/s are possible in stationary water with the power level set on HIGH. Reducing the power level will help to reduce the amount of transducer induced flow at the expense of a reduced signal to noise ratio in the return signal.
A range of options exist for accounting for streaming when it is unavoidable, including measurement of streaming magnitudes with the Vectrino itself and analytical or numerical modeling. For the interested reader; a research article covering acoustic streaming, named “Acoustic Doppler velocity­induced acoustic streaming and its implication for measurement” is available in our web site.

2.4.9 Incorrect Speed of Sound

As already elucidated, the speed of sound in water influences the calculation of the velocity data. The time lag between the transmitted and received pulse determines how far the pulse travelled before it was reflected.
The instruments compute the speed of sound based on the measured temperature (accuracy of 0.1° C). A nominal salinity is assumed, an assumption that works relatively well because the sound speed is more sensitive to temperature variation than it is to salinity variation.
Sound speed errors are typically small, but if you must correct velocity data for errors, use the following equation:
Using a Velocimeter 53
Here, V is the velocity and C is the speed of sound.

2.5 Applications

This section contains typical applications for Velocimeters, and tries to summarize what needs to be taken into account before starting the sampling of data. Also take a look at the Configuration section of the chapter covering your specific instrument for some more details.

2.5.1 Mean Currents

Choose a measurement interval that captures the variations that is of interest. For example, a
typical tidal cycle is well resolved with a measurements every 5, 10, 20 or even 30 minutes.
The cell size has a default setting that corresponds to the instruments transmit frequency. This
may certainly be changed, but be aware that smaller cells increases the measurement
uncertainty, while large cells reduce the measurement uncertainty at the expence of power
consumption.
Vector: Typical moorings allow the instrument to tilt and rotate freely. The Vector measure tilt and
heading and uses this compass information to convert the data to true earth coordinates. How
often the instrument reads the tilt and heading depends on the deployment method used. Buoy
mounted instruments should have the compass set to update relatively fast (every second) so that
buoy motion is accounted for in the velocity estimates. For bottom-mounted instruments, it is
enough with one compass update per burst, while instruments mounted on a mooring line should
update the compass every other second. IMU should of course be considered if mounting the
Vector on a moving structure.
Vector: If magnetic fields are present, consider collecting data in XYZ coordinates rather than
relying on the magnetometer to rotate the results into ENU coordinates. At least, remember to run
a compass calibration.
Salinity should be adjusted in the advanced menu options if it is significantly different from the
default value.
From signal theory we know that the more pings there are within an averaging period, the better
the estimate of the true value we are measuring.
Make sure you are using the most recent software and firmware for your instrument. Visit the
Nortek Web regularly for updates.
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2.5.2 Low Flow Measure ments

An important benefit of the pulse-coherent processing technique is that the instrument can be configured to measure velocities as small as 1 mm/s, or even smaller. This is quite useful in applications where the water motions are minimal, such as in settling tanks, bore holes and in some lakes.
Measuring velocities of a few mm/s or smaller has a few inherent problems that should be considered while planning the measurements:
All Velocimeters are designed to output as much power as possible. This is done to ensure a
strong echo (high SNR) and good quality data in a broad range of applications. However, the high
output power actually generates a non-linear pressure wave that accelerates the water below the
probe. If the horizontal water velocity is small (<10 mm/s), the pressure generates a (negative)
vertical velocity of 1-15 mm/s in the sampling volume. This problem can be minimized by using the
lowest velocity setting, and the lower power setting while measuring low flows. This is referred to
as Acoustic streaming: If ambient flow velocities are of the order of potential acoustic streaming
velocities, acoustic streaming may represent a significant source of bias.
Low flow means low turbulence levels, which may mean clear water. In general, all Velocimeters
have problems measuring in clear water because of lack of scatterers (there is no echo).
Experience shows that unpumped boreholes are difficult while settling tanks usually have enough
scatterers in suspension.
Thermal flows can superimposed on the net transport flow. In some case, the parameter of interest
is not really the point velocity but the net transport rates. If the liquid is not thermally balanced (e.
g, daytime heating) thermal convection cells can be generated. This velocity can be quite strong
(several mm/s) and it can be difficult to detect the lower, net background transport velocity.

2.5.3 Turbulence Measurements

Turbulent flows vary widely, both with distance and with time. Because turbulent flows exist in both large and small scales, acoustic Doppler systems also come in large- and small-scale versions. Systems designed for large-scale measurements have divergent acoustic beams that send sound waves outward, away from the instrument. These systems are not described further in this section, but is covered by the Signature Manuals. Systems designed for small scales tend to have converging acoustic beams that focus their sound waves inwardly towards a small sampling volume, just like the Velocimeters.
The ability to describe a turbulent flow in three dimensions (two horizontal directions and one vertical) is important. The vertical velocity component of turbulent flows is a key contributor to the mixing of different water masses and the exchange of energy, nutrients and particulates. Therefore, the ability to directly measure the rapid velocity fluctuations in the vertical direction is critical for high-quality turbulent-flow measurements.
There are two things to take into account when selecting an instrument to measure turbulence;
1) Sample quickly enough; In order to measure the rapid velocity fluctuations within these eddies, the systems must sample quickly enough to resolve the variations. The importance of fast sampling cannot be overstated. Without sufficient individual (and independent) measurements of the flow, the resulting data will not contain enough detail to describe the phenomenon.
2) Measurement volume; the scale of your measurement volume must match the scale of the turbulence that you are studying. The smaller the turbulence spatial scale, the smaller the measurement volume must be in order to properly describe it. If the scales do not match, you will only capture a portion of the energy within the flow.

2.5.4 Laboratory environments

Follow these guidelines when you mount your instrument in a lab:
Make sure that there are no obstructions between the sensor and the focal point (sampling
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volume).
When mounting your Vectrino or the Vectrino Profiler, use the recessions to strap it to the
structure. Never use the probe stem as mounting point.
Consider the effects of large objects on the flow itself. A rough rule of thumb is that objects disturb
the flow as far as 10 diameters away from the object. Flow disturbance is greatest directly
downstream in the wake behind the object.
All acoustic transducers must be submerged during data collection. Operating your sensor when
the transducers are out of water will not cause any damage, but your data will be meaningless.
For side-looking probes, it is possible to collect 2D-data with only the lower receiver arms
submerged.
Make sure your mounting structure is stable. Small vibrations in the mount can generate large
accelerations in the data.
The best quality is achieved if the main flow direction is perpendicular to the transmit axis. Flow
directly into the transmit axis should be avoided.
To align the Vectrino or Vectrino Profiler in a laboratory flume to ensure alignment of the
coordinate system, here are some tips:
o For a quick setup aligning everything by eye works surprisingly well if you have good references
to align against (flume walls are great for this).
o For a more rigorous setup a post level (two spirit levels mounted orthogonal to one another) can
be used to make sure the mounting fixture and probe are level. This assumes the top of your flume is level since everything is usually mounted on a cross piece to it. If you have a tilting flume this method will not work.
o For a non-standard setup where the probe is horizontal instead of vertical or for side looking
probes, a level of any type is needed to make sure the probe head parallel to the flume bottom or very accurate distance measurements.
o Look at the probe check plot after mounting the probe and filling the flume with water. Tilts in the
head can be identified there based on the return echo from the bottom (as long as the velocimeter can see the bottom). For example, look at the sharp front of the bottom echo and just make sure all the beams see it in the same location.
o As far as rotation of the head, if you have a ruler with a wide enough surface, we use a level with
markings on it's top, you can align the upstream and downstream probe pair at the same distance from one wall. It's also fairly easy to rotate the head once the flume is running and try to minimize the cross stream and vertical components (if this is how your flow is working).
o For example, use zipties to mount the probe head as they will typically allow easier adjustment
and are difficult to overtighten and cause damage to the probe head.
o If you do not mind transforming your data, you can develop a minimization routine that will rotate
and apply pitchs and rolls to the measured velocities to "level" the head by minimizing the appropriate components

2.5.5 Wave Measurements

This section is written with Vectors in mind. Before describing each setup parameter for waves, there are a couple of things to be aware of:
Keep in mind that the location of the pressure sensor is located where the stem is connected to
the unit. This is the location from which one measures the distance off the bottom. It is later
entered as a parameter for the wave processing.
Special consideration must be taken when using a Vector with a cabled transducer array (opposed
to the firmly attached stem type). For the cabled type, it is critical that during deployment the
instrument’s array relative to its body (cylinder) is the same as it is with the Vector with the stem.
This is because the internal tilt sensor determines up or down, and ultimately ensures that the
correct coordinate system is used for the directional estimates.
For more information about waves and wave measurements for the Vector, it is recommended to take a look in this section: Measuring Waves. More details about wave processing can also be found in the manual called Comprehensive Manual - ADCP (available in the web site).
Burst Sampling vs Continuous Sampling: W ave data is collected in a mode that is referred to as
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Burst. Burst sampling mode takes rapid sampling over a specified time interval. Burst sampling is of particular use when there is an interest in sampling a specific part of the energy spectra.
Basic Sampling Requireme nts: Waves are random and therefore measuring waves requires sampling over a period of time that will best “capture” or represent the complete sea state statistically. The objective is to measure the wave event over a long enough time so that the random event can be properly characterized.
Sampling theory suggests, as a rough rule of thumb that the measurement duration is long enough to capture a minimum of 100 cycles of an event (waves, in this context). When we measure ocean waves we have to consider what the longest expected wave period is going to be; 100 cycles of this longest wave will be the minimum wave burst duration.
Number of sample s: This is the number of data samples collected during a wave burst. The optimum choice for number of samples is used in conjunction with the sampling rate where the total burst length in time is considered. As with all measurements there is a trade off between accuracy of the estimates and the consumption of resources (battery power and memory). The consumption is considerably more for wave measurements than current profiles.
Example: If waves are to be measured in the Mediterranean sea, we would expect the waves to be
10 seconds or shorter. Therefore 10 seconds x 100 cycles is 1000 seconds. Sampling rate and
number of samples defines the sampling length. A corresponding configuration could be either
1024 samples at 1 Hz or 2048 samples at 2 Hz.
In order to use Nortek developed waves post-processing software the instrument must be set in burst mode. The number of samples should be set to 1024, 2048, or a number consistent with the chosen sampling rate to ensure over 15 minutes of data is collected.
Sampling Interval: The sampling interval specifies how often the instrument will collect wave data ensembles. This should be specified so that changes in the wave climate can be properly detected. Since wave events are relatively slowly developing events, choosing a relatively long interval make sense. A Typical interval is every hour but may range from 0.5-3 hours depending on length of deployment time and available resources (battery and memory).
Sampling Rate: This is the sample rate for the wave data measurements and it applies to the pressure and velocity measurements. The sample rate represents the absolute upper limit on the resolvable waves. The upper limit is half the sample rate; this is also known as the Nyquist Limit.
Example: Waves sampled at 1 Hz can only resolve waves up to 0.5 Hz, and waves sampled at 2
Hz can only resolve waves as short as 1 Hz. Note that there are other mechanisms, such as
deployment depth, that can have a stronger influence on the frequency limits of resolvable waves.
Choosing the best setting is often used in conjunction with the number of samples. The Vector can sample at 1, 2, 4, 8 Hz, etc. However, note that if one is only interested in measuring waves then it is probably not necessary to sample any higher than 2 Hz. Therefore the upper limit for the length of the data record is 2048 samples. This is due to the fact that the PUV approach can not detect waves much higher than 1 second in period due to the attenuation effects associated with the deployment depth and wave frequency.
If the sampling rate is too slow compared to the time variation of the motions, under-sampling is the result and the data is said to be "aliased" with respect to the wave motion, and the waves cannot be well resolved.
Velocity Range: It is also suggested to set the nominal velocity to no more than +/- 1.0 m/s; where the associated horizontal velocity range is 2.1 m/s (the horizontal and vertical ranges are provided in the Deployment Planning dialogue box). The orbital velocity associated with large waves can reach this speed in shallow water. This may be adjusted downward if waves are expected to be small, or
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adjusted upwards if waves are expected to be exceptionally large.

2.5.6 Near Boundary Measurements

The middle of the sampling volume is positioned approximately 5 cm (or 10 cm on the field probe) below the transmit transducer located at the center of the probe for the Vectrino. For the Vector it is 15 cm, and the measurement volume for the Vectrino Profiler spans from 4-7 cm from the probe (user selectable).
The distance to the boundary shown on the computer display is the distance from the middle of the sampling volume to the nearest boundary. The sampling volume is of finite extent and the minimum distance to the boundary that still permits data collection is 4-6 mm for a standard set-up. Some experimentation is required because the exact limit depends both on the condition of the boundary as well as the exact software configuration.
One thing to note when operating in a flume is that the bottom material can have a huge effect on the data quality. Some tips about what to do in case the bottom material is reflecting too much of the acoustics is described here: Interference from Highly Reflective Bottoms.
Sidelooking Vectrino probe:
There is no minimum distance to the bed with the sidelooking probe - it can physically be sitting
on the bed.
Sidelooking probes do not have the problem of "weak spots" so they are a little more robust to
operate, especially in high flow environments.
They have higher instrument noise in the vertical than in the horizontal.
They are well suited for use in wave flumes.
They have an awful response to flow coming "from behind" the probe.
If only the two lower beams are submerged: It will work in about 2-cm water at low flow rates and
in this case it will give you just the two horizontal velocity components.
When all four beams are covered with water (around 3-4 cm) you can measure all three velocity
components.
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2.6 Common Configuration Scenarios

The signal-to-noise ratio (SNR) is very low.
Vector and Vectrino: SNR should be >15 dB Vectrino Profiler: SNR should be around 30 at the center of the profile and above 20 at the ends, with a parabolic shape peaking at the sweet spot of 0.05 m range. SNR at ranges greater than 0.06 m will drop sharply so attention should be paid to this region of the profile if used.
If low SNR is encountered, try adding scatterers to the water column such as the seeding material
provided with the instrument. Add a little at a time and see if SNR improves.
If there are enough scatterers in the water, check the Power Level in the Configuration dialog and
make sure it is on high.
If the Power Level is on High and scatterer concentration is high enough, but SNR is still low,
please contact support for further guidance.
The velocity time series look spiky and correla tion is low or varies widely.
Correlation should be very high, not widely scattered. For the Vectrino Profiler: Correlation profiles should have the same parabolic shape as SNR. Try and achieve correlations greater than 90% throughout the profile. The highest correlations will be at the sweet spot at a range of 0.05 m, with correlations at ranges greater than 0.06 m dropping off sharply.
To improve correlation, first make sure SNR is high (see points above). Then, check the Velocity Range the Configuration dialog. The actual Horizontal range and Vertical range are reported in the configuration dialog just below where the Velocity Range is set. These need to be appropriate for your flow. If your velocity range is not what you expected, check which ping algorithm is selected. Reported velocity ranges will depend on the algorithm.
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An appropriate Velocity Range for a flow will typically produce a Horizontal Range (m/s) and Vertical Range (m/s) which is larger, but not significantly so, than expected velocities. Horizontal refers to the X and Y instrument velocity components, Vertical to the instrument Z component. Most users will want to match the Horizontal Range to flow conditions. If you expect large velocities aligned with the Vectrino Profiler's Z velocity component, make sure the reported Vertical Range is large enough. Highly turbulent flows (e.g. a turbulent jet) will typically need a larger Velocity Range than mean velocities suggest.
When adjusting the Velocity Range to improve correlation, try moving to a slightly higher value first. In most circumstances a too large Velocity Range is better than a too small Velocity Range.
The Velocity Range is se t appropriately, but there are low correla tion regions in the profile.
These are due to pulse interference, also called weak spots, where a past acoustic pulse's boundary echo is interfering with the current pulse's processing. Weak spots have fairly distinct symptoms. There will be a region of increased amplitude (and SNR) accompanied by low correlations, while velocities will be very spikey and noisy.
For the Vectrino Profiler: The simplest method to deal with weak spots is to use the Adaptive ping interval algorithm mentioned above. Adjusting the velocity range manually will move the weak spot around. If the Adaptive ping algorithm cannot eliminate the weak spot, manually adjusting its position to the least important part of the profile is a good option. Set the Adaptive check: interval to an appropriate value based on measurement conditions. Over a hard boundary where the Vectrino Profiler position is fixed Once will work well. In moving probe or boundary measurements, select an interval reflecting expected time scales for changes in the probe or boundary position.
The Bottom Distance is reporting incorrect values or is noisy (Vectrino Profiler).
In the Bottom Check tab of the configuration dialog:
If available, a physical measurement with a ruler can confirm the bottom distance measurement.
If measuring over a rough boundary, be aware the return echo will be fairly complex and the bottom
distance will be subject to increased uncertainty. Alternative methods of determing bottom
distance will be needed.
Check the Minimum depth (mm): and Maximum depth (mm): values and make sure they span the
expected distance to the bottom.
Check the Cell size (mm): and make sure it is also set to the desired resolution. Larger cells will
create coarser estimates in the bottom position.
If the bottom distance flips between two different values, a second echo is being identified as the
bottom. Check the Center Beam tab in the main window display to see the amplitude profile from
the bottom check ping and look for additional echos at roughly integer multiples of the expected
bottom distance.
Hard bottoms, in particular metal surfaces, can generate strong echos which overwhelm the
receivers and create a very broad bottom peak. This will increase uncertainty in the bottom
location. Set the Gain reduction (dB) to a value which results in the bottom peak having an
amplitude of approximately -10 dB in the Center Beam tab of the main window display.
Probe Check data doe s not look right. One or more of the bea ms has a higher amplitude.
All four beams should show roughly the same amplitude and profile shape.
Check for an obstruction in the beam path. These may be fairly obvious such as a piece of
vegetation or debris. If measuring near objects, such as in the wake of a cylinder, echos from
vertical boundaries may appear in the profiles.
Multiple echos from the bottom reflecting off the surface can also appear in the Probe Check data.
These will typically be at roughly integer multiples of the actual bottom check distance. Depending
on the acoustic path length, an echo closer than the actual boundary position may result.
If there are no obstructions and multiple bottom echos have been ruled out, there may be damage
to the probe head. If there are any signs of damage to your instrument, such as a bent receiver
arm, a bent probe stem for rigid probes, a damaged cable for cabled probes, or damage at the
bulkhead connector on either end of the electronics case, please check the Troubleshooting Guide
for further suggestions.
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2.7 Quality Assurance of Velocimeter Data

Tilt (Ve ctor):
Since there are numerous possibilities for things that can go wrong during a deployment, we need to use the tilt and heading sensors to qualify if the deployment itself went as planned.
The first step is to make sure that the instrument was oriented as intended. This is done by checking the time series of the tilt (Roll and Pitch) and heading sensor data:
If the tilt is large (greater than 10 degrees) then a post-processing option such as “map to vertical”
is encouraged.
Tilt readings between 20° and 30° affect the data accuracy in a way that is likely to make the data
fail to meet the specifications.
Data acquired during tilts exceeding 30° are in general not reliable and should be discarded.
If the tilt or heading measurements change greatly from measurement to measurement (buoy
mounted), it is wise to ensure the instrument was configured with a suitable Compass update rate
(check the deployment file or the header file).
Pressure (Vector):
The next step is to check that the pressure sensor is reasonable. In case of a sudden change in pressure or pressure reading indicating shallower water depth than expected, extra attention should be shown. These events usually occur during the deployment, retrieval, and the occasional curious mariner. Data collected during these events should be avoided in the post processing. If the Vector sample volume is out of the water there is no way to recover velocity data. Data during these periods should fail most data quality checks since the SNR will fall to (near) zero.
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Velocity:
Current measurements that show large variations vertically or vertical structures should be flagged
suspicious unless the measurements are taken in an area where this is expected. The ones that
are most doubtful are those that are physically unrealistic (e.g. 1 m/s changes over a short period
of time). The measurements in a time series that are far from the mean are best to be carefully
inspected.
Raw wave data: The raw pressure signals give an immediate indication about the wave condition;
long waves (T>8 s) give a strong pressure signal and a variation of 1 m in the pressure signal mean
that the wave height is at least the same. On the other hand, a very weak signal in the pressure
sensor (variations of only a few cm) usually means that the waves are small. The raw wave
velocities will appear noisy even at moderate sea states. Only at times with large waves can you
expect a smooth signal. Even so, the noise should not be excessive and it should be possible to
see the wave signal when there are significant wave action on the surface. Watch out for large
jumps or discontinuities.
Vibrations: If velocity spectra show a very large spike at one or more frequencies, it is typically
caused by a vibration in the stem. Wave impact, high flow rates, loose mountings, or vibrations
from nearby equipment will generate vibrations in the probe head. Typical vibrations from
instrument mountings will have a very sharp peak and occur for a very narrow frequency band. The
impact on measurements will depend on what flow parameters are of interest.
Probe Check:
For the Vector: A probe check is made before and after each burst sequence, and also at the very beginning of the sampling when running Continuous mode. After bin to ASCII conversion it ends up in the .pck file as explained in the .hdr file. For the others, probe check can be enabled or disabled. The probe check is designed to act as a measurement quality assurance tool; it lets you inspect the region where the instrument makes it measurements by showing how the signal varies with range.
SNR and Correlation:
SNR and correlation are reported in the data file because they are extremely useful when judging data quality. It is therefore recommended assess overall data quality by looking at SNR and correlation time series and histograms before attempting to interpret the data. Here are some tips:
It is important to note that SNR and correlation is tied to a specific beam velocity measurement,
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not to an orthogonal coordinate direction such as X, and any screening should take this into
account. Therefore, we recommend looking at each beam individually when looking at correlation
and SNR rather than an average across two or more beams. Problems can occur in only one
beam and averaging the data across beams may obscure potential problems.
Check each beam individually. It does occur that just one beam is bad, and this can be indicated
by a signal level near the noise floor, for example. The data may still usable, but if using the
Vector one has to process the data with the two other beams only; a solution that is known as a
two-beam calculation. This will result in 2D currents only (since there is only data from two beams
available. Note that the processing makes one important assumption; the vertical currents are
zero. This is a reasonable assumption in the vast majority of current flow. For the 4-beam
systems, one can discard data from one of the beams and still get 3D velocities out.
Removing low correlation measurements is a good idea because correlation is a strong indicator of
data quality in the sense of a valid Doppler phase shift determination.
Lower correlation means more noise in the data.
The SNR is calculated by subtracting the noise level in counts from the amplitude levels measured
in counts during velocity measurement, and it tells you the rate of signal over noise. The noise
level is measured at the beginning of each burst (and once at the beginning of continuous
measurements). A rule of thumb is that SNR should be >15 dB. The noise level should be around
50 counts for the Vector.
Correlations above ~70% is considered to be generating good quality data. The value of correlation
threshold of 70% is actually fairly stringent and are may be throwing away good data. A close
examination of the dataset is the best way to set a correlation threshold for discarding bad data
points.
Screening data: There is no point using the SNR values to screen data, use the correlation value
instead. W hen you discard data with a low correlation, you are screening the data with respect to
SNR as well.
Typical processing tasks:
1. Assess data quality (QA/QC)
2. Data screening
3. Statistics to describe the flow (mean, variance)
4. Spectral Analysis (turbulence, waves)

2.8 Common Data Analysis Scenarios

Correlation looked good during data collection, but there are se veral range cells with poor correla tion
Low correlation in only a few range cells is symptomatic of weak spots. Unfortunately, there is not a way to correct for this in post processing. Please see the Configuration Guide for how to eliminate weak spots before recording data.
SNR looked good during data collection, but there are several range cells with much different SNR (higher or low er)
This is also symptomatic of weak spots or an obstruction (e.g. an object) within the beam. Weak spots will generally see higher SNR because the strong boundary echo is causing problems, but may be associated with lower SNR depending on the nature of interference.
A beam obstruction will typically produce a strong echo and high SNR. It may create an acoustic shadow resulting in low amplitude and SNR in bins behind the object as well.
Weak spots can not be corrected in post processing. Removing biased velocities associated with an object in the beam is possible by determining which range cells are affected and discarding them from analysis.
Mean velocity profile s do not look good e ven though correlation and SNR are high
It is important to assess data quality and perform some basic quality control on a dataset before attempting to interpret the results. At minimum, discarding very low correlation measurements (<40%, adjusted as needed based on data quality) and very low SNR values (<15 dB, again adjusted
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as needed based on data quality). An outlier filter to remove data which is statistically different than expectations will also help improve the quality of a dataset. Histograms can be quite helpful in determining the effectiveness of any quality control procedures implemented.
Velocity time series are rea lly spiky
This can be caused by many problems, e.g. weak spots, a too small Velocity Range, low SNR. The velocity spikes can be removed in post processing using an outlier filter. In this case, a sim ple hard
threshold discarding velocities, for exam ple > 1 m/s and < 0 m/s, will work.
Velocity changes sign w he n it should not
This is caused by aliasing in beam velocities when the maximum measurable velocity is exceeded. Velocities larger than the ambiguity velocity wrap around to the opposite sign.
To avoid this during data collection, the Velocity Range needs to be set larger than the expected velocities (see Configuration Issues). To aid users in selecting an appropriate Velocity Range, the Configuration dialog reports the horizontal and vertical velocity ranges.
Correcting phase wraps is possible. It involves identification of wrapped velocities and correcting the measured velocity using the reported ambiguity velocity. For details on how to unwrap velocities, check out the relevant section in the Troubleshooting Guide.
Velocity spectra show a very large spike at one or more frequencies
This is typically caused by a vibration in the stem for fixed stem probe heads or the mount a cabled probe head is attached to. Wave impact, high flow rates, loose mountings, or vibrations from nearby equipment will generate vibrations in the probe head.
Typical vibrations from instrument mountings will have a very sharp peak and occur for a very narrow frequency band. Vector fixed stem probes will for example often see a peak around 20 Hz. The impact on measurements will depend on what flow parameters are of interest.
The Vectrino Profiler software provides real time velocity spectra which can help diagnose and correct vibrations. The real time spectra are accessed through the Display time series data. Note real time spectra and imaging can not be used at the same time.
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3 Service Manual

This section covers
Tests that can be performed to ensure that the instrument works as expected
Verification and calibration procedures
Steps to follow if you need to open the instrument for corrective maintenance
It is important to note that when opening the instrument, great care should be taken to keep the sealing surfaces clean and protected from mechanical damage. Only qualified personnel should perform corrective maintenance activities. Please use this Service Manual as guidance and contact us for further assistance.
For Vector users: In this manual, you may encounter a couple of unfamiliar terms: Midlife and Pre­Midlife. The difference between the two is simply when the instrument was produced; pre-midlife are instruments produced before 2009. If you are unsure about what version you have, you can check the firmware version or send us an email with the serial number and we will check it out for you. If your current firmware version number starts with 0.xx or 1.xx, your instrument is a so-called Pre-Midlife version. If your current firmware version starts with 2.xx or above, it is a Midlife version.
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3.1 Function Testing

Always test the instrument before a deployment/measurement sequence to verify that it works as expected. The Final Test Checklist (Appendix A) has been used at the factory for years and is a quick, but good checklist that can be used as a template for the function testing of your system. Also, make sure you have the most recent software and firmware installed. The most recent are always available on our web site.

3.1.1 Initia l Test Setup

3.1.1.1 Power
The first step is to make sure the instrument has a source of power.
Interna l batterie s (Vector)
The internal battery pack is located inside the pressure case. Nortek alkaline battery packs use 18 AA cell batteries at a nominal starting voltage of 13.5 VDC.
Note that the battery pack inside the pressure case is disconnected when sent from Nortek. Refer to the Changing a battery pack section for instructions on how to connect or change a battery pack.
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The voltage of alkaline batteries falls quickly at the beginning, slowly during most of its life, then again quickly at the end. Thus, a 13.5 VDC battery pack will spend most of its life somewhere in a voltage range of 10.5-12.5 VDC. Find more information about the Nortek Batteries at our web site.
The instruments are shipped with an external power supply, which we recommend you use for all but the final testing. If you leave the instrument collecting data, it will continue to run until the batteries are dead. Always make sure to stop data collection when testing is complete.
External power
You may supply power with the external supply that is delivered with the system, or you can use your own external supply. If you use your own supply, be sure the voltage does not exceed the voltage specification for your instrument. Check out the data sheet for your specific instrument for exact requirements, which is also available on the web.
Vector power range: DC input 9-15 VDC Vectrino power range: DC input 12-48 VDC Vectrino Profiler power range: DC input 12-48 VDC
Vectors: If you want to use an internal battery as a backup battery: The instrument will pick the power source with the highest V. If using an external supply of 15 VDC and an internal battery of
13.5 V, the external supply provides a higher voltage than the battery pack, which prevents the internal pack from discharging. Then, if external power fails, the internal battery pack takes over and sustains operation.
The power and battery lines are diode protected, so you do not have to worry about wiring the instrument power backwards - this will not damage your instrument.
3.1.1.2 Converter
A compatible converter is included with all instruments. Currently there are two USB converters that are guaranteed to work with the instruments:
USB/RS232: the FTDI model US232R
USB/RS422: Altronix AL310
Connect the serial cable to the converter, and insert it into the USB drive of the computer. For first time use, give the converter enough time to install its driver correctly. If the driver is not installed
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properly, find the link to the updated driver version on our website.
3.1.1.3 Connect cables
Plug the appropriate ends into the instrument and to the computer via the converter, and make sure the computer connector does not easily fall out.
Before deployment: Protect the cable connector by applying a thin layer of silicone lubricating spray to the pins before you plug it into the instrument. We recommend the 3M Silicone Spray. Grease is not recommended. For Vector users: Remember to protect unused connectors with dummy plugs (relevant for Vectors). For more information about how to protect the connectors, check out the
Connector Care section.
Cable Wiring
See tables describing the pin assignments for the wires and connecors in the Cables and Wires section. If you have a special cable, contact Support to get the correct information.
3.1.1.4 Start the appropriate softw are
Find the instrument specific software on the USB stick that came with the instrument, or download it from our Software and Firmware site (www.nortekgroup.com/software), and install in on your PC. Nortek Windows programs run on all versions since XP (SP3), including Windows 8.
Installing instrument software does not require a license key. After installation is done, start the software and proceed with the following:
1. Select Serial Port from the Communication menu to specify the port number to use. If you are
unsure about which port number to use, check the Device Manager on your computer.
2. Baud rate: You are allowed to set two baud rates. The primary baud rate setting applies to normal
communication and data transfer. The standard baud rate is:
2.1. For the standard Vectrino program, the default baud rate is 19200.
2.2. For Vectrino Plus, the default baud rate is 57600.
2.3. For the Vector, the default is 9600.
2.4.For the Vectrino Profiler, 937500 is recommended and we recommend that you use this baud rate unless you have a good reason to change it.
You can also set a separate baud rate for data download and firmware upgrades (the "download/ configuration baud rate"). A higher baud rate speeds up large file transfers and is appropriate when you have a short serial cable and a relatively noise-free environment. To change the baud rate and make it permanent, do the following:
2.5.Connect the instrument to your computer.
2.6.Set the baud rate in "Communication", "Serial Port" to the baud rate you prefer. Start a deployment, and then stop it. The last step makes the new baud rate permanent. If you remove power and reapply it, the instrument will re-awake with the new baud rate. NOTE: If data download is interrupted, the instrument may be left with a baud rate setting other than the one used for normal communication. When the software tries to establish communication in such cases, it may spend a few moments searching for the current baud rate.
3. Check communication: Verify communication by clicking the “Check Communication” button. The software will automatically find the instrument and read its current setup parameters. Alternatively, select Communication > Terminal Emulator, and press "Send Break". The instrument should respond with a message presenting information about the model of your instrument plus the firmware version number and the mode the instrument is in. If you get a string of garbage characters, try another baud rate setting. If the instrument fails to respond, the software can auto­connect to the instrument. Press Stop Data Collection and wait until the instrument has been found.

3.1.2 Sensor Checks

The first step when performing sensor checks is to set the instrument to collect data continuously. Find the Deployment planning dialog by clicking Deployment > Planning or the corresponding toolbar button.
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Start the test deployment by clicking On-line -> Start Data Collection or click the Start Data
Figure : Vector cable pr obe and fixe d
stem w ith vertical tilt sens or s in upright
pos ition.
Figure : Vector cable pr obe and
fixed ste m w ith horizontal tilt
se nsor.
Collection toolbar button.
3.1.2.1 Temperature
Test the temperature sensor by confirming that the temperature reading is realistic. The temperature reading should be close to the room temperature, assuming the instrument has been in the room for a while to allow for the long time constant.
Specifications:
Range: -4°C to 40°C Accuracy/Resolution: 0.1°C/0.01°C Time response: 10 min for the Vector, 5 min for the Vectrino and Vectrino Profiler
3.1.2.2 Tilt or IMU (Ve ctor)
The tilt sensor is located on the electronic boards inside the housing. The tilt sensor orientation is set in accordance with the system orientation during normal operation.
The standard instrument is designed for vertical orientation. That means that you should make sure the Vector canister is in an upright position. The tilt sensor detects up/down orientation - that means that you can use the Vector pointing up or down and the instrument will know.
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Tilt sensors in probes designed for horizontal orientations will be mounted at right angles.
Uncertain about whether your Ve ctor is with vertical or horizontal tilt?
If the tilt (pitch and/or roll) as indicated in the Sensors’ pane is unrealistically far from 0° when the canister on a table (upright or lying down), the Vector is of the other type.
Verifying tilt sensor:
1) Click the Sensors tab on the main screen of the software.
2) Hold the instrument as level as possible to check that the tilt reading is close to zero.
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Figure : Pitch and Roll definitions
3) Find the X-marking on the probe (which defines beam 1) or canister (on cable probe system) and let X point away from you.
4) Tilt the instrument to about 10 degrees to the right, and verify that the roll reading has a positive sign, and that the value is around 10 degrees.
5) Tilt the instrument to about 10 degrees to the left, and verify that the roll reading has a negative sign, and that the value is around 10 degrees.
6) Tilt the instrument about 10 degrees forward, and verify that the pitch reading has a negative sign, and that the value is around 10 degrees.
7) Tilt the instrument about 10 degrees backward, and verify that the pitch reading has a positive sign, and that the value is around 10 degrees.
8) Turn the instrument upside down, and perform steps 2-7 again. Note that the signs will still be the same, assuming that X is still pointing away from you.
Also confirm that the last status bit changes from 0 to 1 when the probe orientation is changed from pointing down (as the figure above) to pointing up. For the Vector the instrument is defined to be in the UP orientation when the communication cable end of the canister is on the top of the canister, ie when the probe is pointing down (as in the figure above). Be aware that when the Vector is running in Continuous mode, the Vector needs to be oriented in the correct orientation when starting it – up/ down orientation will not be updated while measuring. When the Vector is running in Burst mode, the orientation is checked/updated at the beginning and end of each burst.
Specifications:
Accuracy/Resolution: 0.2°/0.1°
3.1.2.3 Compass (Vector)
The compass measures the earth's magnetic field. Combined with the tilt sensor on the head, the compass enables the instrument to obtain heading information. These data makes it possible to convert velocity measurements to Earth coordinates. Without a compass, the instrument still measures the tilt.
To test the compass:
Hold the instrument away from any magnetic influence (like metal objects, cell phones etc.) Point X towards North Slowly rotate it clockwise around Z, and verify that the compass reports increasing degrees (0, 90,
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Figure : Rotate
the ins trum ent
to ve rofy
com pas s
functionality.
Clockw is e is
pos itive
180, 270 and then 360/0 - corresponding to North, East, South and West respectively) Click Stop Data Collection, invert instrument, click Start Data Collection and repeat the procedure.
Remember to perform a Compass Calibration before deployment, to account for magnetic interference near the instrument.
3.1.2.4 Pressure (Vector)
To test the pressure sensor:
1) Set the pressure sensor depth to 0.2 m in the On-line > Set Pressure Offset dialog.
2) Place the instrument in a suitable container filled with water (approximately 0.5 m deep)
3) Verify that the pressure reading is correct; with the instrument submerged to 0.5 m, and with an offset of 0.2 m, the pressure sensor should read 0.7 m.
An alternative way to test whether the sensor is functioning is by forming a seal around the sensor with your mouth and blowing to observe an increase in pressure.
Have in mind that the pressure sensor is not a depth meter. Due to atmospheric pressure variations, the sensor signal may have an offset. Therefore, remember to set a Pressure offset before every deployment.

3.1.3 Noise floor

First, check the noise level of the instrument. See the readings in the software, under the Current tab. Pinging in air should produce signal strengths (amplitudes) of
45-55 counts for Vector 50 counts for the Vectrino and the Vectrino Profiler
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When the instrument pings in air, the velocity measurements will be the noise floor. The signal values above are therefore referred to as the noise floors. Data from all beams should show a similar noise floor. Note: Background noise is very prone to interference from nearby sources, such as a power supply. During testing make sure the instrument is far enough away from other electronics.
Put the instrument in a bucket of water and observe the signal strength and the velocity. The signal strength should rise noticeably (the actual level depends on the size, shape and material of the bucket), and the velocity data should appear less noisy. If the velocity graphs remain weak even with the probe in water, try varying the position of the probe or add some seeding to the water in the form
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of dirt or small particles.
Deep Water versions (titanium housings) of the Vectors are prone to noise in human environments, so you may see a higher noise floor than the above listed. This will not be a problem in the field/in water.

3.1.4 Beam Amplitude and Velocity Checks

The following checks should be carried out in a suitable volume of unobstructed water. We recommend carrying out initial testing in a test tank, which is both convenient and provides a controlled environment. If there are insufficient scatters in the water, some seeding material may be necessary.
3.1.4.1 Amplitude
1) Change the coordinate system to beam Coordinates by choosing BEAM as Coordinate system in the Deployment Planning menu.
2) Start the test deployment by clicking Online > Start Data Collection or click the corresponding toolbar button.
3) Click the Amplitude tab (bottom of display) to observe the amplitude of all the beams on the graphic display.
4) Immerse the instrument so that all the transducers are submerged. Note the amplitude of each beam, displayed in counts. All the beams should have similar amplitude, within 10 counts of each other.
As an additional check, each beam can be blocked in turn, by either holding each transducer out of the water (while keeping the others immersed) or by covering each transducer with a suitable acoustic attenuating material such as dense plastic, or even a finger. The amplitude of the blocked beam will fall to around the noise level, while the others will remain unaffected.
When blocking the transmitter, the receivers should report nothing other than noise.
3.1.4.2 Velocity
1) Change the coordinate system to XYZ by selecting XYZ as Coordinate system in the Advanced Deployment Planning menu.
2) Start the test deployment by clicking Online > Start Data Collection or click the corresponding menu button.
3) Click the Velocity tab to observe the X, Y and Z velocities on the graphic display.
4) Move the instrument backwards and forwards at a constant velocity through the water, along the X-axis. A positive and negative deflection of the X-axis velocity should be observed on the graphic display, while the Y- and Z-axis velocities should remain around 0 m/s. Repeat the procedure for the Y- and Z-axis. Ensure that the displayed velocities are reasonable.
Read more about coordinate systems in the Principles of Operation, where you will find Beam, XYZ, and ENU definitions. Note that the X-axis engraved or clarified in form of a colored indicator on the head/probe of the instrument always points in the direction of beam 1 and a positive X-axis.
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Figure : Vector de finitions of X-axis. Note the red (or on som e versions Black) labe l on the X-arm of the
Figure : The probe che ck function show s how the signal varies w ith range. The thre e colore d graphs
corr e s pond to each of the thre e ve ctor r eceive beams. A is the tr ans m it puls e . B is the area around the
measurement volum e . C is a bottom e cho. Graphs are scaled in m m distance from the tr ans m it
transduce r , parallel to the transm it beam .
3.1.4.3 Probe Check
Designed to act as a measurement quality assurance tool, the Probe Check function in the software lets you inspect the region where the instrument makes its measurements by showing how the signal varies with range. You can use it to diagnose and correct problems and to optimize data collection. To start the Probe Check:
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Ve ctor.
1) Make sure the instrument is submerged in water.
2) Click Online > Start Probe Check. For the Vectrino Profiler, enable the check in the "System" tab.
The actual sensing volume is a relatively narrow region within the broad peak indicated by B. It is for the Vector centered at sample 100-105 and normally extends across +/- 3 counts from the center. If the probe check outputs look very different from the figure above, check the Troubleshooting Guide before taking further action. You can find probe checks that display and describe different problems
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in the Probe Check section.

3.1.5 Test Recorder Function (Vector)

You can test the recorder with the same set-up as above.
1) Start data collection with "Test" followed by "Start With Recorder".
2) Write a name to use for the file you will record internally.
3) After a few minutes, stop the data collection.
4) Retrieve your data by clicking "Deployment" followed by "Recorder Data Retrieval".
5) Convert it to ASCII by clicking "Deployment" followed by "Data Conversion".
6) Review the collected data with an ASCII text editor (i.e. Notepad).
If you leave the instrument collecting data, it will continue to run until the batteries are dead. Always make sure to stop data collection when testing is complete.
It is a good routine always to start a new deployment with an Empty Memory. Before you erase the recorder, make sure that you have transferred all the data you want to retain to your computer and that the data is in good shape. Then click Deployment > Erase Recorder.
Note: The maximum number of files that can be stored in the File Allocation Table (FAT) is 31 on all Nortek instruments. The "Syslog" takes one spot, so the maximum number of files with measurements is 30.

3.1.6 Battery degaussing

All fasteners and hardware are non-magnetic and the magnetic signature of the internal electric components is low. The exception is the alkaline battery pack. Therefore, the batteries are degaussed before sending them, and also recommend the user to degauss the batteries before using them.
The calibration routine will compensate for magnetic masses whose field strength, and orientation relative to the compass, do not change. If the field produced by a magnetic source close to the compass changes significantly over the course of the deployment, heading errors may be the result.
There is no need to degauss Lithium batteries.

3.2 Customer Calibration

All instruments have what we call head matrices that are unique; it describes the geometry of the sensor probe, or the transducer orientation to be more specific. The matrices are computed during the velocity calibration done during production. As long as the sensor probe are not physically deformed, the head matrices will, consequently, remain the same. Further, what is measured by the sensor is the change in frequency from the acoustic pulses sent out through the water to those being reflected back. In other words, a slight change in center frequency will not affect the measured frequency shift, or the Doppler shift, which is entirely depending on the velocity of particles in the water. Therefore the sensors never need to be re-calibrated for current speed and direction, unless they are physically deformed.

3.2.1 Compass Calibration (Vector)

Each compass has been calibrated at the factory to quantify the characteristic response of the individual components and of the system as a whole. When it leaves the factory, each system can measure its tilt and the direction of its magnetic field vector accurately, anywhere in the world. However, users disturb the magnetic field near the instrument when they deploy. Adding a battery pack and mounting the instrument with deployment hardware adds magnetic materials that change the magnetic field measured by the instrument. The compass calibration procedure quantifies this magnetic disturbance, and the instrument's compass algorithm then corrects for it to obtain accurate heading.
The user should perform a compass calibration just prior to deployment to correct for the introduction
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Figure : Successful r otation of a com pass calibr ation.
of new magnetic materials. The compass calibration procedure requires a single, slow rotation around the instrument's tilt axis. A rotation taking at least 60 seconds is sufficient. For the calibration procedure to work, the compass and all magnetic materials must remain fixed relative to each other. As long as this is the case, the calibration procedure can correct for magnetic field disturbances that are greater than the earth's magnetic field. You should conduct this procedure outdoors, away from other possible magnetic elements that will not be part of the mounting structure during deployment.
The procedure:
1) Assemble the frame (or similar) with the instrument, battery canister, and extra ballast, etc. and connect the system to the computer.
2) Make sure the frame is level when calibrating the compass, and that it is possible to rotate the entire system 360° horizontally.
3) Click On-line > Compass Calibration.
4) Click Start and rotate the entire system slowly around the Z-axis of the instrument. An example of a successful rotation is shown below. Note that when doing this in the field, you cannot expect to end up with a circle as perfect as this one. However, we recommend you to do this slowly in an attempt to come as close to the ideal circle as possible.
5) To utilize the obtained values, click Done. You will be prompted to confirm that the new values shall be transferred to the instrument to serve as the new compass setting.
As a side note, the compass is not used when measuring velocity in XYZ or beam coordinates, but if you plan on using the compass heading at a later point (for instance to orient the XYZ velocities relative to the lake axes), it is probably worth calibrating the compass in advance.

3.2.2 Set Pressure Offset (Vector)

The pressure sensor offset is not calibrated to, nor corrected by the atmospheric pressure. This means that the pressure sensor reading will follow the atmospheric pressure, thus the sensor signal may have an offset. Atmospheric changes can vary the depth reading as much as 0.3 m. Note that all data on the recorder will be erased during this procedure. To set the Pressure Offset
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Figure : Set Pres s ure Offs e t dialog
Figure : Stable pre s s ur e reading and the title indicate s
succes s
1) Connect the instrument to a computer and submerge the instrument to a known depth.
2) Click Online > Set Pressure Offset and key in the depth in m. The below figure shows the dialogue box for setting the pressure offset.
3) When the pressure has a stable reading, as in the screenshot below, click Done.
.
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3.3 Working Inside an Instrument

A. Remove the four #6-32 x ¾’’ titanium screws and washers holding the end cap to the pressure case and remove the endbell.
B. Disconnect the 2-pin connector and pull the battery out of the pressure case.
C: Insert the new battery into the pressure case and reattach the 2-pin connector.
D: Reattach the endbell to the pressure case and mount with four titanium bolts and washers. Make sure that there are no dust or particles on the O-rings on the endbell, and that they are whole. Also, be careful so that the internal wires are not squeezed between the endbell and the housing. See Recommended torque when securing screws - you do not need to fasten them too much if you have the POM housing
E: Test the instrument by collecting data without using an external power source to ensure that the battery is properly connected. Make sure to stop data collection so that the instrument will power down after you are through testing it.
A. Remove the four #6-32 x ¾” titanium screws and washers holding the end cap to the pressure case.
B. Disconnect the 2-pin (battery) and 9-pin (harness) connectors
C. Pull the battery out of the pressure case.
D. Remove the #6-32 x ¾” titanium screws and washers holding the
When opening the instrument, great care should be taken to keep the sealing surfaces clean and protected from mechanical damage.

3.3.1 Changing a Battery Pack (Vector)

The following procedure outlines how to connect the battery or to install a new battery. A fresh desiccant bag should be included in the pressure case, as humid air can condense enough water do damage the electrical circuitry.
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Because the battery pack uses standard alkaline batteries, you normally do not need to observe any special precautions and/or procedures when you dispose old batteries. Caution! If you have lithium batteries, keep in mind that you must be very careful and that disposal requires special precautions and/or procedures. Rules for disposal of batteries, especially lithium batteries, vary from country to country.

3.3.2 Accessing the Circuit Board (Vector)

The following procedure describes how to access the circuit board, necessary tools can be found in the supplied toolkit.
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probe head to the pressure case.
E. Carefully, slide out the probe with the circuit board attached. Do not put a lot of pressure on the probe itself, as the connection between the sensor head and head board represent the weakest point. Pull/push the main board instead.
1. Recorder / ProLog
2. Screws / Bolts
3. Standoffs
4. Nuts
5. Lock Washers
A. Access the circuit board.
B. Loosen the four (relatively short) screws and remove the compass board from the main board
C. Insert the four long screws (2) through the holes in the corners of the compass board, and then through four standoffs (3). Carefully insert the screws through the holes on the main board, and then through four more standoffs. Make sure the connector between the compass board and the main board ‘Clicks’.
D. Carefully position the Recorder board (1) (image to the right) and fit it gently to the matching connector on the main board (image to the left).
When reassembling the system, the following is important:
Make sure that there are no dust or particles on the O-rings on the head or the endbell, and that they are whole. A fresh desiccant bag should be included in the pressure case, as humid air can condense enough water do damage the electrical circuitry. Be careful when sliding the circuit board into the pressure housing; it is easy to make scratches, and these scratches may cause instrument leakage. Attach the probe to the housing with the titanium bolts. Make sure the bolts have both a spring washer and a flat washer. Insert and connect the battery, and attach the endbell. Make sure that also these bolts have both a spring washer and a flat washer. Read also about Recommended Torque for securing screws.

3.3.3 Installing a Memory Board (Vector)

When ordering a memory upgrade from Nortek you will receive the following:
To install it, follow the procedure as described below
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E. Secure the assembly with lock washers (5) and nuts (4).
G. After reassembling the instrument, erase the recorder, and check that the system reads the correct recorder size.
3.3.3.1 Installing a Memory Board - Pre-midlife (Vector)
1. Long nylon screws
2. Mounting blocks
3. Short nylon screws
4. Nylon nuts
5. Threaded metal bolt
6. Nylon standoffs
7. Recorder board
A. Start with accessing the circuit board (Section 1.3.2).
B. To remove the compass board, start removing all screws and blocks with the exception of the right mounting block on the main board, as shown in the image. The point is to add two new mounting blocks (2) as support for the recorder board.
C. Screw the metal bolt (5) through the mounting block (2) in the correct hole (indicated in the image).
D. Screw the two blocks from (C) through the holes in the main board and through another mounting block on the opposite side of the board (both new blocks is to be placed on the same side of the main board). NOTE that the block on the ‘compass’ side of the card sticks out over the edge of the board, whereas the block on the ‘recorder’ side do not.
Please note the positions of the various holes in the mounting blocks: Make sure that the twin holes are positioned ‘away’ from the center of the main board. It is essential that they are positioned correctly.
E. Insert the two long nylon screws (1) through two of the holes in the compass board, then through the nylon standoffs (6). Continue with carefully inserting the screws through the two holes (at the opposite side of the mounting blocks) on the main board. Attach two more standoffs, and carefully position the recorder. Make sure the connector between the main board and the recorder board ‘clicks’. Apply a little LocTite to all plastic screws.
When ordering a memory upgrade from Nortek you will receive the following:
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F. Fix the recorder and the compass boards to the mounting blocks with the short nylon screws (3). Apply a little LocTite to all plastic screws. Cut off excessive length on the long nylon screws.
G. Connect the compass and the main board with a connector (see image in point E, to the upper right)
H. After reassembling the instrument, erase the recorder and check that the system reads the correct recorder size (Section 1.5.3).
C(2). Attach the cable to the main board before fixing the recorder to the main board.
C(3) Attach and bend the cable as shown, to avoid cable getting caught while inserting the instrument into the housing.
A. Remove the endbell and remove the batteries (if relevant)
B. Connect the DC/DC harnesses to the instrument harness. There is only one of the two molex connectors pictured that will fit.
C. Slide the DCDC carefully into the canister
D. Connect the second molex connector to the endbell
E. Reattach the endbell to the pressure case and mount with four titanium bolts and washers. Make sure that there are no dust or particles on the O-rings on the endbell, and that they are whole. See
Recommended torque when securing screws - you do not need to
fasten them too much
F. Check that it is working. Take note of the voltage limitations/ requirements of your updated system!
A. Access the circuit board
B. Loosen the four screws and remove the compass board from the main board
3.3.3.2 Installing a Memory Board With Cable - Really Old Pa radopps
Some of the older systems will not fit the connector between the main board and the recorder, and thus need an additional cable. The recorder board looks a little different, but it is essentially the same process as described above. Two steps are added:

3.3.4 Installing a DC/DC (Vector)

When installed in an instrument, a DC/DC converter is used to downconvert the supply voltage to 15 V.
To install one; open the instrument just as you would when replacing a battery pack (Changing a
Battery Pack). The DC/DC takes the place of one 50Wh battery pack

3.3.5 Installing IMU sensor (Vector)

When ordering an IMU upgrade from Nortek you will receive the a small electronics board that needs to be mounted on the main PCB. It will physically replace the existing compass board
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C. Re-use the four screws and the standoffs
D. Place the IMU board on the standoffs, and secure with the nuts.
E. Check that the connection cable between the board and the IMU is properly fixed
F. Update the Headfile for the instrument
G. Update the firmware of the instrument
H. Update the software version
I. Test the instrument
A. Access the circuit board
B. Unscrew the two screws that hold the harness in place
C. Press the little tap on the connector, and pull the harness off.
D. Attach the connector of the new harness.
E. Align the mounting blocks at the round disk with the holes on the main board. Add a little LocTite and fasten.
F. Add a thin layer of silicone grease on the harness’ O-ring.
G. Carefully insert the system back into the housing.

3.3.6 Changing the Wiring Harne ss (Vector)

You will find the necessary tools in the toolkit that came with the instrument; 7/64” and 1/16” hex driver and silicone grease. Use LocTite as described below, if accessible.

3.3.7 Changing the Output Power for Auxiliary Sensors (Vector)

You can change the output voltage level that is supplied to external sensors. This is typically needed if an external analog sensor (e.g. OBS) operates in a specific voltage range and the raw battery power does not fall within this range. The default output voltage level is RAW (battery or external adapter).
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Voltage level
Command
Max current
RAW
OPWRBA
500 mA
+5V
OPWR5V
250 mA
+12V
OPWR12
100 mA
Voltage level
Resistor position
Max current
RAW
R270 (default)
500 mA
+5V
R268
200 mA
+12V
R269
50 mA
3.3.7.1 Midlife Electronics
Midlife electronics change the power levels with a simple command in the terminal emulator:
3.3.7.2 Pre-midlife Electronics
You can change the output voltage level that is supplied to external sensors. This is typically needed if an external analog sensor (e.g. OBS) operates in a specific voltage range and the raw battery power does not fall within this range. The default output voltage level is RAW (battery or external adapter). This can be changed to +5V or to +12V by changing the position of a 0-W resistor. The three resistor positions share one pad so the modification should be straightforward.
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3.4 Changing a Probe

A. Start with the procedure described in Accessing the Circuit Board
If you are working with a pre-midlife Vector; remove the two bags of Desiccant taped around the board and gently disconnect the ground strap on the reverse side of the board.
B. Unscrew the two screws fixing the main board to the head board, and pull the probe away from the board.
D. Reassemble the instrument.
E. Load a new headfile into the instrument as described in Replacing Heads/Boards
F. Set pressure offset
Vector:
The following procedure outlines how to change a probe. You will find the necessary tools in the toolkit that came with the instrument; 7/64” and 1/16” hex driver and silicone grease. Note that the procedure for changing a transducer head also includes updating the instrument’s head configuration file.
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After changing a Vector probe, it is a good idea to run a simple function test before deploying.
Vectrino and Vectrino Profiler:
Swapping probes on the Vectrino/Vectrino Profiler platform is pretty easy, as all probe configuration information is located on the electronics fixed to the probe. A few things to note:
The trickiest part is to connect the connector on the head board onto the main electronics. Aligning them and position the probe carefully is our best advice. Twisting the probe slightly will reveal whether the connection was successful or not. If the O-ring seal has fastened, a small (careful) side-to-side rocking is needed. The bolt patterns will make sure that there is only one way for the new probe to be attached. Once the probe is seated, do not overtighten the bolts. Run a probe check to confirm that everything works as intended. A firmware upgrade is not necessary when replacing probes. A firmware upgrade is not needed when replacing probes. The calibration information used to convert from beam coordinates to XYZ is stored in the probe electronics. When the Vectrino/ Vectrino Profiler firmware starts up, it reads this information directly from the probe, so you do not have to worry about changing anything from the firmware point of view after the probe head has been changed. Swapping from a lab probe to a field probe requires nothing extra than the simple swap. Swapping probes between a Vectrino and a Vectrino Profiler is not possible.

3.5 Upgrade Firmware

By the term firmware we are referring to the internal software of the instrument, as opposed to the instrument software running on a PC. When you purchase a brand new instrument, it has a firmware version matching the PC software, hence no firmware upgrade will be needed before you start using the instrument. However, new functionality (and in rare cases bug fixes) is likely to be offered in the future, requiring that the firmware is upgraded. New firmware is posted at the Nortek web. You will need to register to get access, but access is quick and free of charge.
Remember to transfer data that you would like to retain to your PC before you upgrade the firmware,
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any data acquired in the instrument will be erased to avoid inconsistencies.
To do the Upgrade:
Download the firmware that applies to your instrument. Connect the instrument to a PC. In the instrument software, select Configuration > Firmware Upgrade… Browse and select the new firmware file and click ‘Open’.
If you are asked for a license key, you can find it on the flash disk that accompanied your instrument. If you cannot locate it, contact Nortek for a new key.
Upgrade to Vectrino Plus (Vectrino only):
The Vectrino Plus firmware is protected by a license key. So the first step is to contact the local Nortek representative to get hold of a license key.
Next:
Download the Vectrino Plus firmware from the web site. Download the Vectrino Plus software from the web site. Connect the instrument to a PC. In the Vectrino Plus software, select Configuration > Firmware Upgrade… Browse and select the new firmware file and click ‘Open’. Add the license key when prompted. Check that the Plus version is reported in the "Firmware" display in the software.

3.6 Erase Recorder (Vector)

Connect the instrument to a PC. In the instrument software, select Deployment -> Erase Recorder.
Recorder wear may occur when a large number of write/erase operations are issued. The exact number may vary between instruments but is specified to 10,000 files. This means if the recorder is erased each time then 10,000 deployments can be done before having to replace the recorder.
The flash circuit on the main PCB is closely linked to the recorder. Read more about that here.

3.7 Update Headfile (Vector)

Most of the sensors in a Nortek instrument have to be calibrated to keep the specified accuracy. This and the fact that we offer flexibility in probe geometry, deployment orientation and external output/inputs make it necessary to store a number of parameters to make the instrument perform as intended. All of this is stored in the headfile. It is actually misguiding to call it a headfile; it has parameters that are dependent of the instruments electronics as well. We make the file when producing the instrument, and it is saved in the respective instrument (we also keep a copy at Nortek).
Here is a list of the calibration parameters that are stored in the headfile.
Serial no. Pressure sensor calibration data Tilt sensor calibration data Beam to XYZ transformation matrix (conversion between the coordinate systems) The transducer frequency No. of beams Tilt sensor orientation Compass alignment data Temperature sensor calibration data Compass calibration data
The last two are dependent of the instruments electronics - not the probe head.
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The head configuration file is sent from us to you upon request. When you have received the .bin file, proceed with the following:
Connect the instrument to a PC. In the instrument software, select Configuration > Sensor head. Browse and select the new headfile and click ‘Open’.
When the head file is configured, it is important to:
Set the pressure offset Level the instrument and confirm the tilt reading
The probe configuration file must be updated whenever the probe has been replaced.
In certain troubleshooting situations Nortek Support may ask you to download your current head file. To do so follow these steps:
Connect the instrument to the PC and start instrument software. In the Terminal Emulator click Log File and give the file a descriptive name. Type GH, which is short for Get HeadFile, and Send. Stop logging the file. You have now captured the data necessary for a head file. Remove the last two binary characters (06 06 which is acknowledge). Save the file as a *.bin.

3.8 Mechanical Aspects and Maintenance

Preventive maintenance is your primary tool to keep your instrument in shape and ready for action and deployment. We recommend a regularly scheduled procedure which will act as a preventative measure to ensure your instrument continues functioning as intended. The following sections can be used as a maintenance guideline for the components that may be exposed to wear and tear.
Only qualified personnel are allowed to perform corrective maintenance activities. Please contact Nortek for further assistance if any doubt.

3.8.1 Mechanical Tolerances

Watertight sealing of the instrument housing is provided by double O-rings on the head and endbell sub-assemblies. The outer O-ring forms the primary seal and the inner forms a secondary (or backup) seal. When opening the instrument, great care should be taken to keep the sealing surfaces clean and protected from mechanical damage. Keep water out of the open pressure case. Both fresh and salt water can corrode the circuitry.
If the instrument has been subjected to environmental conditions outside the specified design limits, mechanical tolerances may be affected.

3.8.2 Instrument Care

The Nortek instruments are intended for use in water. Other fluids may have an adverse effect on the plastic materials used. If using the Vectrino/Vectrino Profiler lab probes in saline water, it is recommended to keep the deployment time short and to clean the probe with clean water after the deployment. The material used on the probe is Stainless steal, but we have seen signs of corrosion on probes used in saline water and would therefore emphasize that this is not a useage that the Vectrino/Vectrino Profiler probe has been designed for. Using the field probe is the recommended solution.
For prolonged storage at elevated temperatures close to or at the specified limit, or when temperature control is uncertain, it is recommended that the screws securing the end caps to be loosened in order to minimize the risk of any deformation due to temperature/stress condition over time.
Do not use the molded head or endbell as a clamping surface, always clamp to the instrument
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housing.

3.8.3 Recommended Torque for Securing Screws

When installing end caps and sensor heads, care should be taken when tightening the screws.
1. Just a little tension on the screw is needed.
2. When the O-ring starts to be compressed, turn each screw a little at a time until the O-ring is fully compressed.
3. Tighten the screws diagonally. Tightening one screw fully before continuing on to the next may cause improper O-ring seating and very high mechanical stress concentrated around the screw hole. This may cause leaks and/or damage to the head or the endbell.
4. The screws only need to be tightened sufficiently for the O-ring and spring washers to be fully compressed.
Figure : a) "Tw o-fingers " tighte ning of scr e w s. Indicator arr ow show s pos ition be fore final tightening. b) Final tighte ning 30-45 degrees from "tw o-finge rs" tightening.
Over-torqueing has no positive effect and may damage the threads and/or area around the screw holes on the head and endbell. Keep in mind that ocean pressure holds the end cap tightly – all the screws have to do is to keep the end cap from falling out when the system is above water.

3.8.4 Connector Care

It is extremely important to keep underwater connectors clean and well lubricated. W e recommend before plugging in connectors, always blast the pins with compressed air, inspect them for cleanliness and then lubricate with 3M Silicone Spray. Do not use the silicone grease included in the toolkit on connectors, as this is intended for O-rings only.
Before deployme nt:
Demate the connector set. Flush the connector set with fresh water or compressed air, remove dirt. Inspect for damage, corrosion and cuts. Apply a thin film of 3M Silicone Spray or equivalent. Mate the connector halves and check if they are properly mated.
Afte r deployment, before storage:
Flush the connector set with fresh water or compressed air, remove dirt. Inspect for damage, corrosion and cuts. Mate with dummy plug if available.

3.8.5 Cable Care

Avoid nicks and cuts around connector points, as these are the sealing surfaces. Elastometers can be seriously degraded if exposed to direct sunlight or high ozone levels for extended periods. Do not pull on the cable to disconnect connectors, pull the connector itself. Avoid sharp bends at cable entry to connector. Ensure that the cable is fixed to the mounting fixture to avoid mechanical stress to the connection.
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3.8.6 O-ring Care

Watertight sealing of the instrument housing is provided by double O-rings on the head and end cap sub-assemblies. The outer O-ring forms the primary seal and the inner forms a secondary (or backup) seal. If the integrity of the O-rings are degraded the instrument should not be re-deployed. In this case, please contact us.
O-rings are the critical component that keeps water out of the housing and thus the instrument dry. Make a routine of O-ring inspection, maintenance and replacement.
Check the O-rings and the O-ring grooves for grit, hair, lint, sand, or anything that could potentially breach the O-ring seal. After frequent deployments or if O-rings or groves appear dirty, remove O-rings and clean the groves. To remove O-rings, use finger pressure or the rounded edge of a plastic card to lift the O­ring out of the grove. Caution! Never use a metal object to remove an O-ring. It may cause damage to the O-ring or the sealing surface. To check O-rings for damage, place the O-ring between the middle and index finger and thumb. Then pull the O-ring through your fingers, feeling for any debris or wear. If O-rings are dirty, it is best to replace them. Washing dirty O-rings with soap and water is not recommended. Soap breaks down the lubricants and will compromise the integrity of the seal. Properly greased O-rings will help maintain sealing integrity and minimize O-ring degradation. Use enough grease to lubricate the O-ring thoroughly, but not so much that it will attract additional debris. Clean the groove with a lint free swab or the folded edge of a paper towel.
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3.8.7 Repla ce Desiccant Bag

Humid air can condense enough water do damage the electrical circuitry. At least once a year, replace the desiccant located in the pressure case or the external battery canister. Refer to the
battery installation description for the procedure of opening the pressure case.

3.8.8 Biofouling

Marine growth, or fouling, on moorings should be considered when planning long-term mooring systems. The thickness of growth depends on location (temperature, sunlight conditions, depth, latitude, currents etc.). Fouling can be a problem already after 2 weeks in tropical areas or it can take 6 months in cold areas. Sunlight is also an important factor - fouling is generally much less of a problem below 100 m than it is at 5 m depth.
When calculating forces, the marine growth is accounted for by increasing the expected weight and diameters of the mooring line and all instrumentation attached, in addition to increasing the drag.
Antifouling paints and other agents are often used to avoid transducers being covered with barnacles or other evil crustaceans during long deployments. The important thing when it comes to antifouling is that the paint is not too thick; otherwise, the signal strength may decrease. We tested the effect on the profiling range of the 2 MHz Aquadopp and we could find no appreciable change when we applied a thin (1 mm or so) layer on the transducers. You can probably use most anti-fouling paints as long as it is not too (chemically) aggressive and contains no solids (metal flakes, etc.) that could interfere with acoustic beams.
We realize barnacle has to be removed mechanically, but we strongly advice against using sharp objects capable of harming the surface. We also recommend staying away from strong organic solvents such as acetone.
A common, easy, and inexpensive way to keep the Delrin housing on the Vector clean is to wrap the housing in either clear packaging tape and/or clear plastic wrap (such as the brand name "Seran Wrap"). At the end of the deployment, simply unwrap the protective coating to find a clear instrument. Tapes such as "Duct Tape" can leave a sticky residue that is very difficult to remove (although it does not actually harm the Delrin housing).
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Underwater Connector
Termination
Pin. No
Wire Color
Purpose
Pins
Description
3
Black
RS232 Tx
Twisted Pair
24White
RS232 Rx
3
5
Black
RS232 Gnd
Twisted Pair
5
6
White/ Purple
Power Output
Red wire
7
Black
Analog Ch. 2
Twisted Pair
Green wire
8
White/ Orange
Analog Ch. 1
Yellow Wire
1
Black
Power Gnd
Twisted Pair
Black Wire 2
White
Power +
Red Wire
Screen terminated at pin 1 in underwater connector, unterminated at PC side.
Ref: N2100-002A

3.9 Cables and Wires

This chapter gives you the wiring for the most common cables. The wiring is the same if the connector is circular or square. In addition there is a table below describing the harness and the 24 pin connector at the electronics board. This might be handy if there is need to change the wiring harness without time to receive one from Nortek.

3.9.1 Vector

RS232 with option for Analog input:
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RS 422. Note that Tx and Rx refer to the instrument and not the PC:
Underwater Connector
Termination
Pin.NoWire Color
Purpose
Pins
Description
3
Black
RS422 Tx +
Twisted Pair
74White
RS422 Tx -
27Black
RS422 RX -
Twisted Pair
8
8
White/ Orange
RS422 RX+
3 5
Black
Sync. Out
Twisted Pair
Black Wire
6
White/ Purple
Sync. In
Green Wire 1
Black
Power Gnd
Twisted Pair
Black Wire
2
White
Power +
Red Wire
Screen terminated at pin 1 in underwater connector, unterminated at PC side.
Ref: N2100-108
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Underwater Connector
Termination
Pin.NoWire Color
Purpose
Pins
Description
3
Black
RS232 Tx
Twisted Pair
24White
RS232 Rx
35Black
Ground
Twisted Pair
5
6
White/ Purple
Analog Z*
Red Wire 7
Black
Analog X
Twisted Pair
Green Wire
8
White/ Orange
Analog Y
Yellow Wire 1
Black
Power Gnd
Twisted Pair
Black Wire
2
White
Power +
White Wire
Scr een
Bare
Ground
3 bare wires for grounds, connected internally to power ground.
Ref: N2100-004
Wiring of RS232 with option for analogue outputs:
*Optional version outputs pressure instead of Z-Velocity
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3.9.2 Vectrino

Pin no
Wire color
Function
Termination
1
White
X2Black
Y3White/Grey
Z14White/Purple
Z25White/Black
Gnd (analog)
6White/Blue
Sync+
7
White/Green
Sync-
8
White/Yellow
Gnd (digital)
DSUB, pin 5
9
White/Orange
Tx
DSUB, pin 2
10
White/Red
Rx
DSUB, pin 3
11
White/Brown
Power -
Power supply connector
12
Black/red
Power + (12-48V)
Power supply connector
Ref: N2100-303
Figure : Vectrino
conne ctor and
draw ing
highlighting the
pin numbe ring
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Wet-end termination
Try-end termination
Underwater connector
Pin.NoWire Color
Descript ion
Pin
Connector
(PMCIL-12-MP)
1
White
Rx+
3
DB-9 connector, pin 1 and 5 are grounded.
2
Black
Rx-
8
3
White/ Grey
Tx-24
White/ Purple
Tx+
7 5
Not used
6
White/ Blue
Sync-
Terminal block
7
White/ Green
Sync+ 8
Not used
9
Not used
10
Not used
11
White/ Brown
Power Ground
Jacket
2-pin Jack plug
12
Black/ Red
Power +
Center
Shield
Power Ground
Connected internally to Power Ground
Ref: N2100-304: RS422 cable for Vectrino Profiler
Figure: Harness and harness
pins

3.9.3 Vectrino Profiler

3.9.4 Using Long Cables (Vector)

3.9.5 Harness (Internal wiring)

RS232 data communication at 9600 baud will normally work fine for cables up to 50 m long, depending on the environment. If you want to run a longer cable, you can switch to RS422 by installing a different wiring harness you can get from Nortek.
You can also try using RS232 with longer cables by reducing the baud rate. Keep in mind that RS422 is a more reliable means of communication than RS232 – changing environmental conditions could cause RS232 communications to fail over a long wire without apparent reason.
You should consider voltage drop across the cable, particularly if you use the two highest power settings. Design your power supply and cable so that the voltage stays below 16 VDC and never falls below 9 VDC.
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Pin
Function
1
Power Ground
2
+ External Power Supply
3
Power Ground
4
+ Battery Supply
5
X Analog Out
6
Y Analog Out
7
Z Analog Out
8
Auxiliary Analog Out
9
CTD Power Out
10
Signal Ground
11
RS232 Tx
12
RS232 Rx
13
CTD RS232 Tx
14
CTD RS232 Rx
15
Analog In 1
16
Analog In 2
17
RS422 Tx+
18
RS422 Tx-
19
RS422 Rx+
20
RS422 Rx-
21
Sync Out
22
Sync In
23
+3.3V LP
24
RS422 3.3V Supply (grounded for RS232, shorted to pin 23 for RS422)
Relevant for Vectors only
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4 Integrators Guide - Light

This section covers:
Analog Inputs - relevant for the Vector Analog Outputs - relevant for the Vector and the Vectrino Synchronization - relevant for all the velocimeters
This chapter cover the subject on how to use Nortek instruments together with other instruments or sensors.
For a more comprehensive Integrators Guide, check out the one we have available here: https://www.
nortekgroup.com/manuals-quick-guides. The Integrators Guide provides the information needed to
control a Nortek product with a non-PC controller. It is aimed at system integrators and engineers with interfacing experience. There is one for Vector and Vectrino (called Intergrators Guide - Classic), and a separate one for the Vectrino Profiler.
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4.1 Analog Inputs (Vector)

Voltage Level
Command
Maximum Current
RAW
OPWRBA
500 mA
+12 V
OPWR12
100 mA
+5 V
OPWR5V
250 mA
There is an option to connect external sensors to the two analog inputs. The external sensors may be powered by the Vector (enable this in the Deployment Planning dialog), and their data output may be stored in the instrument during a deployment or downloaded in real time. With two external sensors connected, the Vector is able to read both analog inputs at the same time.
The reported analog value from the Nortek instrument is counts. The scaling is V = (Counts/65536)*5 due to 16 bit AD converter. The input range is 0-5 Volt, where 0 Volt equals 0 counts, 5 Volts equals 65535 counts and 2.5 Volts equals 32768 counts.
The analog input can be scaled and re-labeled in the instrument specific software; Click View > Analog Inputs.
To configure the Vector for use w ith external sensor:
In the instrument software click Deployment > Planning > Use existing or use Load from Instrument. Check the “Use Advanced Settings” box and go to the Advanced tab. Define which analog input (1, 2 or both) to use. There is a choice between fast and slow sampling. W hen choosing slow, the sampling is done once a second together with the other non-velocity sensors. If fast is chosen, the analog sensor is sampled together with the velocities at for instance 8 Hz. Only one Slow input is permitted. If you want to power the external sensor from the instrument you must check the Output power box.
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The output power is configured in hardware by Nortek and can be raw (i.e. battery power), +5 V, or +12 V (see table below). The raw setting is the default setting and all instruments come with this setting unless otherwise was specified upon ordering.
Power out can be software selected by sending a HEX command in a terminal emulator.
Be aware that the power out is turned off when the instrument is in sleep mode, as this contributes to reducing the system’s power consumption significantly. Consequently, the external sensor used must be capable of automatically resuming its duties once the power comes back and it must do this within 1 sec after power up in order to provide correct data for the first sample. Also note that:
Power at 5 and 12 VDC comes through switching regulators. This means that power drawn from the battery pack is 15-18% greater than the power consumed by the external device. See example below when considering energy consumption. The output voltage is protected against short-circuit with a 1-amp fuse. To protect the Vector circuitry against external sensors providing an output voltage in excess of +5.0V, there is a clamping diode on the input with a current limiting resistor in series. The diode will conduct at voltages above approximately 5.3V. To achieve stable conditions during testing, the +5V_SEN net can be powered up from command mode by sending the hex command 435001C4. The output voltage turns on at least 0.8 s before the beginning of a measurement interval, and it turns off again at the end. The first measurement of the analog inputs occurs roughly 0.9 s after power is applied. The planning software does not consider power consumption of your external devices when it plans
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deployments. The data from the external sensor will not be affected by the instrument data quality. For example, the external sensor’s data will be totally unaffected even if the instrument is out of water and thus measuring noise only.
The input impedance of the analogue inputs is 468 kΩ/100 nF
Example: This example explains how to calculate energy consumption. It covers the energy consumtion of an OBS3+ sensor, 15 mA, 5-15V supply, that are set up for 30 days deployment. Duty cycle of OBS: (2048samples/4Hz)/1200sec measurement interval = 43%.
1. Output power voltage set to battery: 11V*15mA*43% = 71mW per sensor. Energy per sensor: 30days*24hours*0.071W = 51 Wh. That is 102 Wh for two OBS sensors.
2. Output power voltage set to 12V: 1.25*12V*15mA*43% = 97 mW per sensor. Energy per sensor: 30days*24hours*0.097W = 70 Wh. That is 140 Wh for two OBS sensors.
3. Output power voltage set to 5V: 1.25*5V*15mA*43% = 40mW per sensor. Energy per sensor: 30days*24hours*0.040W Hi Frans, = 29 Wh. That is 58 Wh for two OBS sensors.

4.2 Analog Outputs

The Vector and Vectrino have the option of outputting data represented as analog signals. They are able to output the measured velocities on a linear scale, and the voltage output is 0-5 volt. This voltage must manually be converted to velocities:
0 m/s is reported as 2.5V
-velocity range as 0V +velocity range as 5V.
Available outputs are 3 velocities (E/X/B1 N/Y/B2 U/Z/B3) and pressure. For standard cable only 3 outputs are available, thus 3 velocities are default.
In both the Vector and the Vectrino, the scaling output for the velocities is chosen in the deployment planning. It is important to select an analog range that matches the velocity range. You could in principle use an analog range of +/-7 m/s and a velocity range of +/- 1 m/s, but you would lose a lot of precision. The best thing is to first decide what maximum velocity that you want to measure and then select the minimum velocity range and analog output range that includes that velocity.
Note: To use this function Nortek needs to provide a head file with analog outputs enabled. The correct harness also needs to be installed. Contact Nortek for more information.
Example : The maximum expected vertical velocity is 0.8 m/s, and the the maximum horizontal velocity is expected to be 2.3 m/s. Configuration: Select the +/- 2m/s velocity range
Select the +/- 2.5m/s analog range If the expected maximum horizontal velocity had been 2.9 m/s instead, you could still use the +/­2m/s velocity range, since the maximum horizontal velocity would then be 3.5 m/s. But you would then need to use the +/- 7m/s analog output range to be able to represent the velocities from 2.5 m/s to 2.9 m/s with the analog output voltages. Note that the velocity range is different in the vertical and horizontal direction whereas the analog output range is the same for all components, beam, XYZ or ENU.
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The velocity is given by:
Where vel_range = full range of velocity, V_range = usually 0V to 5V, V_out = voltage outputted, vel_min = minimum velocity.
Alternatively set up two equations (2 unknowns, slope and intercept) using mx + b = y, where x is voltage and y is velocity. Knowing voltage and velocity in two scenarios will give m and b (use max and min velocity and voltage). This gives you the full linear fit.
At zero flow the outputted voltage should display 2.5V. If not, there may be issues with grounding.
Example : The range is specified to +/- 1m/s. Voltage outputted is 1V, V_range is 5V. The velocity
would be: (2/5V)*1V-1m/s= -0.6m/s

4.2.1 Vector

Vectors can send out velocity signals as 0-5 VDC analog voltages. Here is what is required to enable analog outputs:
A special wiring harness passes the analog voltages out to the external connector. The output
wires include three signal wires and one ground wire (which is shared with the RS232 ground). The
remaining wires are allocated to RS232 and power.
A special head configuration file where analog outputs is enabled is needed.
Enable analog outputs in the Vector software's planning menu (Advanced Tab). The planning
module controls data collection in the Vector the same, whether or not the analog outputs are
enabled.
Once in analog output mode, you can remove and reapply power as desired. When you reapply
power, the analog outputs resume. Allow a few seconds for the instrument to start up after you
apply power.
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(vel_range/V_range)*V_out - vel_min = velocity

4.2.2 Vectrino

Vectrino can send out only velocity signals as 0-5 VDC analog voltages, 3 channels standard, one for each velocity component. Here is what is required to enable analog outputs:
Enable analog outputs in the Vectrino software's planning menu. The planning module controls
data collection in the Vectrino the same, whether or not the analog outputs are enabled.
Once in analog output mode, you can remove and reapply power as desired. When you reapply
power, the analog outputs resume. Allow a few seconds for the instrument to start up after you
apply power.
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Figure: Sampling Interval

4.3 Synchronizing with Other Instruments

It is possible to synchronize instruments together, or its sampling can be controlled by other sensors. This comes in handy if there is a need to use several instruments for a single set of measurements.

4.3.1 Vector

Sync out (Vector acts as Master)
The Vector can be synchronized with other instruments via the SyncIn and SyncOut. The synchronization option requires that the correct wiring harness is installed in your system. The SyncOut signal consists of 1.95 ms long, 3.3V pulses that can be configured for two different schemes of output synchronization. The selection of the type of SyncOut signal is made on the Advanced tab in deployment planning:
If Output Sync for other sensor is selected, the SyncOut pulse will be output in the middle of each
velocity-sampling interval.
If Output Sync for Vector is used, the SyncOut pulse will be output at the completion of each
sampling interval.
In addition, one SyncOut pulse will be output when the sampling of velocities is started.
Sync In (Vector acts as Slave)
The SyncIn signal permits external control of the sampling. There are three possible modes of operation that can be set for Input Sync:
No Sync. In this mode, the Vector ignores the SyncIn signal and data collection starts under
software control only.
Start on Sync. In this mode, the Vector starts data collection on the rising edge of the SyncIn
signal. Sampling of velocities then proceeds at the set sampling rate. After data collection is
started the SyncIn is ignored.
Sample on Sync. In this mode, the Vector outputs a sample after every rising edge of SyncIn. To
use this mode, the Start on Sync mode must be used as well. Therefore, the first rising edge
starts the averaging process for the first sample only. The first data sample is output on the
second rising edge of SyncIn. The output data at each rising edge of SyncIn will correspond to an
average since the previouis rising edge of the SyncIn. The Vector must be configured with the
setup software for a sampling rate that is equal to or higher than the sampling rate that will be
used.
Example: If the signal on the SyncIn input to the Vector is generated to correspond to a sampling
rate of 25 Hz, the Vector should be configured in software for a sampling rate of 32 Hz. In most
cases, it will be sufficient to synchronize different Vectors using Start on Sync.
Instruments shipped after November 2000 are fitted with a real time clock with an accuracy of ±1 min/year over a temperature range of 0–40 °C. Over a burst period of for example 1 hour, the maximum clock drift between two Vectors will then be 13.7 ms. Since they will operate at the same
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Figure: Description of sync and sampling and data out intervals
Figure: Inout threshold values for SyncIn
temperature the clock drift is likely to be even smaller. At 8 Hz sampling rate, this will be 1/10 of a sampling interval over one hour of measurements.
Output of the Vector system data (compass, tilt and temperature) is not synchronized between different Vectors through the use of the SyncIn signal. Instead, the start on the sync edge that is present in both synchronization modes is used to start the 1 Hz output of the system data. Each Vector will then output its system data based on its internal real time clock. This implies that the number of system data outputs may vary slightly from one instrument to another. Note that this is not a problem for the synchronization of the velocity measurements. The compass and tilt data are used internally in the Vector to ensure correct transformation of the velocities to earth coordinates when ENU is selected as coordinate system. In detail, each Vector configured for Start on Sync will output system data in a certain order at the start of continuous measurement and at the start of each burst when configured for burst measurements. The system data are output in the following order:
1. Output header containing noise measurements and date/clock.
2. Output one sample of system data.
3. Wait until external trigger is detected and then start to output system data at a 1 Hz rate based
on the local clock. Velocity data will be output according to the configured synchronization scheme.
Specifications of Signal Levels
The SyncIn input voltage must be between 0 V and 5.0 V. The SyncIn is a Schmitt Trigger input with
a pulldown resistor of 100kΩ to ground. The input threshold values for the SyncIn are:
Vt+ input positive threshold, 2.2 V
Vt– input negative threshold, 0.9 V
The output voltage levels for the SyncOut are:
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Figure: Output voltage levels for SyncOut
Voh high level output voltage, min 2.5 V
Vol low level output voltage, max 0.45 V
There is spike protection on both signal ports but there is no filtering on the input port. It is important to consider noise issues (ground loops, etc) as noise may cause an unwanted start on sync trigger.
Example 1: Running three Vectors with synchronized sampling of velocities in continuous mode.
Connect the SyncOut line from one Vector to the SyncIn line on the two other Vectors.
Connect the ground cables together.
Choose Output Sync for Vector for the first Vector. This will be the master.
In the setup for the two other Vectors that will be slaves, check both boxes in the Input Sync
(Start on sync and Sample on sync).
With the rest of the setup identical for the three instruments; start the two Vector slaves first. When the master Vector then is started, it will trigger the start of the other two Vectors.
Example 2: Running three Vectors with synchronized sampling of velocities in burst mode.
Connect the SyncOut line from one Vector to the SyncIn line on the two other Vectors.
Connect the ground cables together.
Choose Output Sync for Vector for the first Vector. This will be the master.
In the setup for the two other Vectors that will be slaves, check both boxes in the Input Sync
(Start on sync and Sample on sync).
Use identical setup for the rest of the configuration parameters for all three instruments.
Synchronize the clocks in all the Vectors.
Start Recorder Deployment for the master Vector setting the deployment time to the time when
you want the instrument to start (for example 4.00.00 p.m. or 16.00.00 – exact time format
depends on your computer’s settings).
Start Recorder Deployment for the two slave Vectors setting the deployment time to the
deployment time of the master Vector minus 10 seconds (in this example 3.59.50 p.m.). The two
slave Vectors will now wake up in each burst 10 seconds ahead of the master Vector. After
outputting the burst header and one set of system data they will then wait for the start on sync
trigger from the master Vector so that all three instruments will start the data acquisition
simultaneously (in this example at 4.00.00 p.m.). The two slaves will then continue taking data at
the identical rate of the master Vector as they receive the sample on sync triggers from the
master Vector.
The same procedure can of course be used if only synchronized startup is required. The only difference is that the Sample on sync box in the Input Sync configuration must be left unchecked.
Example 3: Starting three Vectors simultaneously from another instrument
Connect the SyncIn signals from the three Vectors together with the sync output line from the
instrument providing the start on sync signal.
Ground all the four instruments together.
Using identical and desired setups for the three Vectors start all of them with the Start on sync
option configured.
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Generate the start on sync trigger from the other instrumentation.

4.3.2 Vectrino

The Vectrino can serve as master for other Vectrinos, or its sampling can be controlled by other sensors. If one connects a controller to the Vectrino, a fairly sophisticated system in which the controller can power the Vectrino and provide it with sync pulses to control the sampling accurately can be set up. The controller can serve as a storage device.
Note: A Vectrino can operate as a master for a Vector, but the opposite is not possible.
The Vectrino can be synchronized with other instruments via a pair of sync lines. To avoid noise problems and to make cabling easier, the two sync lines are RS485 which is balanced and bi­directional. The sync lines are labeled Sync– and Sync+. Some instruments have incorrect labels on the sync lines, if the labels read Sync in and Sync out they should be treated as Sync- (Sync In) and Sync+ (Sync Out). The polarity is not too important as the sync scheme is quite insensitive to the polarity.
Firmware version V1.30 Plus supports synchronisation of transmit pulses to avoid both electric and acoustic interference when operating several Vectrinos together. This feature is only available in the Plus version.
Integrators Guide - Light 97
How Synchronization Works
Output Sync (Vectrino operating as the master) transmits a pulse on RS485 with a duration of 40 µs.
Sync+ for Vectrino transmits the pulse by the end of the sampling interval and a single pulse at the beginning of the first sampling interval to start everything. For other sensors, Sync+ transmits a pulse at the middle of the sampling interval. Input Sync triggers on any edge, rising or falling, on
RS485. After each trig, the input is discarded for the next 64 µs.
RS485 levels
These levels define the signal the Vectrino reads for Input Sync:
High level: Sync+ > Sync– by 200 mV
Low level: Sync+ < Sync– by 200 mV
Synchronizing Multiple Vectrinos
Connect all the Sync+ lines together and all the Sync– lines together. All instruments should
share a common ground.
Select one instrument as the master and the rest as slaves (Input sync) in the software.
Start data collection in all slaves before starting the master. The slaves will then wait for the first
sync pulse from the master before sampling commences.
If you use Sample on sync, all instruments should be configured with the same sampling rate.
We have checked that there is no interference between Vectrinos once they are properly synchronized but have not tested how close they can be during operation. An intelligent guess is that they should be at least 5-10 cm apart to avoid acoustic interference.
Example : Synchronizing From a TTL Source TTL signal levels can be mixed with the RS485 levels of the Vectrino:
Connect your sync pulse to Sync+ and connect Sync– to a constant voltage, 1.5 volts for
instance. This provides a defined transition when the TTL signal changes, which is not the case if
you ground Sync–.
When Vectrino functions as master, the Sync+ line can be connected to the TTL input and the two
systems must be connected so they share common ground.
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Noise problems: If you encounter noise problems, try terminating the Sync+ line at the TTL input by connecting a 120 ohm resistor in series with a 1nF capacitor between the Sync+ line and ground. The best solution for external sync is using RS485 as the input/output device.
Example : Vectrino master and Vector slave
Connect ground of the two systems together
Connect Sync+ on the Vectrino to SyncInput on the Vector
Configure the Vectrino with the desired velocity range, 30 Hz sampling rate and select output sync
for Vectrino and check the box for master
Configure the Vector with the desired velocity range, continuous sampling, the next higher
available sample rate (so 32 Hz in this example) and check the boxes for start on
sync and sample on sync
Select the file name for disk recording in both software instances and make sure you also start
disk recording in both software instances at this point.
Press Start Data Collection in the Vector software
Press Start Data Collection in the Vectrino software
The measured data will now be shown on the display and stored to file, properly synchronized.

4.3.3 Vectrino Profiler

The Vectrino Profiler can serve as master for other Vectrino Profiler's, or its sampling can be controlled by other sensors. This comes in handy if there is a need to use several Vectrino Profilers for a single set of measurements. Note that the Vectrino Profiler can operate as a master for a Vector, but the opposite is not possible.
If you connect a controller to the Vectrino Profiler, you can set up a fairly sophisticated system in which the controller can power the Vectrino Profiler and provide it with sync pulses to control the sampling accurately. The controller can serve as a storage device. The Vectrino Profiler System Integrator Manual is a useful source for this type of applications.
The Vectrino Profiler can be synchronized with other instruments via a pair of sync lines. To avoid noise problems and to make cabling easier, the two sync lines use an RS485 chip which is balanced and bi-directional.
The sync lines are labeled Sync- (n) and Sync+ (p). Note that on some of the older instruments the sync lines are labeled Sync In and Sync Out. These should be treated as Sync- (Sync In) and Sync+ (Sync Out).
How Synchronization Works
Output Sync (operating as the master) transmits a pulse with a duration of 50 µs. The Vectrino Profiler transmits a pulse at the end of the sampling interval and a single pulse at the beginning of the first sampling interval to start everything when in "Master (Vectrino)" mode. W hen in "Master (Other)" mode, a pulse is transmitted in the middle of each sampling interval.
Input sync triggers on the falling edge if the Sync+/Sync- signal. After each trigger the input is
discarded for the next 100 µs.
Specifications of Signal Levels
RS485 levels: These differential levels define the signal the Vectrino Profiler reads for input sync;
High level: Sync- > Sync+ by 200 mV
Low level: Sync- < Sync+ by 200 mV
Example : Synchronize Multiple Vectrino Profilers
1. Connect all the Sync+ lines together and all the Sync- lines together. All instrument should share
a common ground.
2. Select one instrument as the master and the rest as slaves (Input Sync) in the softwares.
3. Start data collection in all slaves (Click the Start Collecting data icon) before starting the master.
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The slaves will then wait for the first sync pulse from the master before the sampling commences.
If you use Sample on sync, all instruments should be configured with the same sampling rate.
Example : Synchronizing form a TTL source TTL signal levels can be mixed with the RS485 levels of the Vectrino Profiler.
1. Connect your sync pulse (0-V volts) to Sync- and connect Sync+ to a constant voltage V/2
(Where V is the ON voltage of the sync pulse). This provides a defined transition when the TTL signal changes, which is not the case if you ground Sync+. The Sync inputs are diode limited to 5V through a 4.7 ohm resistor. Input voltages above 5V are not recommended for use.
2. When the Vectrino Profiler functions as master, the Sync- line can be connected to the TTL input
and the two systems must be connected to share common ground.
Noise problems: If you encounter noise problems, try terminating the Sync- line at the TTL input by connecting a 120 ohm resistor in series with a 1nF capacitor between the Sync- line and the ground. The best solution for external sync is using RS485 as the input/output device.
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5 Troubleshooting Guide

This section covers:
Tests that can be performed if you encounter a problem
What to do if your data does not look right
Instructions on how to return an instrument for repair
This section contains our yearlong experience in where to start looking if an instrument does not behave as intended. If you encounter a problem, you should:
Work in a systematic way and do not neglect the obvious.
Get a good overview of the problem; make notes during the troubleshooting process.
Start by looking for simple causes such as incorrect baud rate, power not connected, bad
connections or incorrect serial port. If the system involves custom cables, power supply or the
like, first assemble and test the instrument using just the cables and battery that came with the
system. This is the easiest way to get the system to work, and if you have trouble, you can
always return to this setup to confirm that problems are not caused by a faulty instrument.
If you still have problems after consulting this guide, please contact our subsidiaries, sales representatives or Nortek Support. To help us in giving good support, please
be specific about the error – a screen shot is often helpful
include if possible
o an error description
o a picture, if possible
o firmware and software version
o serial number (head ID, hardware ID or order number)
o a raw sample file showing the error
o the collected data set showing the error
o result of tests as loop-back, current drain and LED signaling
o Vector/Vectrino: screen-shot of the performed probe check
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