Datawell BV Wave Unit Reference Manual

Wave Unit

Reference Manual

April 15, 2019

Service & Sales

Voltastr aat 3
1704 RP Heerhugowaard
The Neth erlands
 [phone]
 [phone]
www.datawell. nl

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Declaration of conformity

(According to EN ISO/IEC 17050-1:2004)

Document No.: Datawell_DoC_Wave_Unit_1_1

Manufacturer's name: Datawell B.V.
Manufacturer's address: Zomerluststraat 4

2012 LM Haarlem
The Netherlands

Declares under sole responsibility that the product:

Product name: Waverider
Trade name: Datawell
Model: Wave Unit

complies with the essential requirements of the following applicable European Directives,
and carries the CE marking accordingly:

EMC Directive (2004/108/EC)
RoHS Directive (2011/65/EU)

and conforms with the following product standards:

Standard Limit

EMC EN 300 220-1 V2.4.1 (2012-05) −54 dBm, 47-74, 87.5-118, 174-230, 470-862

MHz
EN 300 220-2 V2.4.1 (2012-05) −36 dBm, <1000 MHz, −30 dBm, >1000 MHz
EN 300 390-1 V1.2.1 (2000-09) −36 dBm, 30 MHz-1 GHz
EN 300 390-2 V1.1.1 (2000-09) −30 dBm, 1-4 GHz
EN 301 489-1 V1.9.2 (2011-09) / 3 V/m, 80-2700 MHz
EN 301 489-3 V1.4.1 (2011-09) 4 KV/8 KV contact/air

EN 55022: 2010 / 40 dB(μV/m), 30-230 MHz
EN 61000-6-3: 2007 47 dB(μV/m), 230-1000 MHz

EN 55024: 2010 / 3 V/m, 80-2700 MHz
EN 61000-6-1: 2005 4 KV/8 KV contact/air

Supplementary Information:

This DoC applies to above-listed products placed on the EU market after:

Jan 1, 2017 Eric Stoker
Date Quality Assurance Manager

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Contents

1 Introduction ................................................................................................... 7

2 Maintenance ................................................................................................... 9

2.1 Consumables ........................................................................................... 9

2.1.1 Bags of drying agent ......................................................................... 9

2.2 Inspection ................................................................................................. 9

2.2.1 Damage ............................................................................................ 9

2.2.2 Opening the Wave Unit and sealing rings ......................................... 9

2.3 Service ..................................................................................................... 9

2.3.1 The Wave Unit’s wave motion sensor ............................................... 9

3 Trouble Shooting ......................................................................................... 11

3.1 Wave Unit diagnosis .............................................................................. 11

3.2 The Wave Unit motion sensors .............................................................. 11

3.2.1 Stabilized platform and accelerometer ............................................ 11

4 Repair ........................................................................................................... 13

4.1 Calibration .............................................................................................. 13

4.2 Contact ................................................................................................... 13

4.3 Serial numbers ....................................................................................... 13

5 Reference ..................................................................................................... 15

5.1 Dangers and warnings ........................................................................... 15

5.1.1 Dangers .......................................................................................... 15

5.1.2 Warnings ......................................................................................... 15

5.2 Measuring waves with the Wave Unit .................................................... 15

5.2.1 Measuring waves - Considerations ................................................. 15

5.2.2 Wave Unit parts .............................................................................. 16

5.2.3 Packing ........................................................................................... 16

5.2.4 Stainless steel housing ................................................................... 16

5.2.5 Lid Assembly ................................................................................... 17

5.2.6 Lid ................................................................................................... 17

5.3 Wave motion sensors ............................................................................. 18

5.3.1 Wave height, principle of measurement .......................................... 18

5.3.2 Wave direction, principle of measurement ...................................... 18

5.3.3 Wave Unit axes and references ...................................................... 19

5.3.4 Inspection of the fluid level .............................................................. 20

5.3.5 Sensor fluid and temperature .......................................................... 21

5.3.6 Calibration of the vertical accelerometer ......................................... 21

5.3.7 Platform offset and stability ............................................................. 21

5.3.8 Magnetic compass .......................................................................... 21

5.3.9 Pitch and roll ................................................................................... 22

5.3.10 Horizontal accelerometers ............................................................ 22

5.3.11 Filtering ......................................................................................... 22

5.4 Data processing ..................................................................................... 24

5.4.1 Wave height spectrum .................................................................... 24

5.4.2 Wave direction spectrum ................................................................. 25

5.5 Data format ............................................................................................ 27

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5.5.1 Wave Unit serial message format ................................................... 27

5.5.2 Datawell real-time format ................................................................ 28

5.6 Stainless steel housing and lid assembly ............................................... 31

5.6.1 Installation ....................................................................................... 31

5.6.2 Packing, weights and dimensions ................................................... 31

5.6.3 Wave Unit housing .......................................................................... 31

5.6.4 Handles ........................................................................................... 31

5.6.5 Lid, serial number and FS direction ................................................ 31

5.6.6 Drying agent bags, plywood ............................................................ 32

5.6.7 Lid and connections ........................................................................ 32

5.7 Power supply and consumption ............................................................. 34

5.8 Contacts and Questions ......................................................................... 34

5.8.1 Addresses ....................................................................................... 34

5.8.2 Telephone and fax numbers ........................................................... 34

5.8.3 Email-addresses ............................................................................. 34

5.8.4 Website ........................................................................................... 35

5.8.5 FAQ ................................................................................................ 35

5.8.6 Datawell Bulletin ............................................................................. 35

5.9 Literature ................................................................................................ 35

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1 Introduction

The Datawell Wave Unit is an OEM version of the well-known Directional Waverider Mk-III
for measuring wave motions in three directions. The unit gives out the real time heave, north
and west displacements as well as common wave parameters like Hs and Tz and spectral data.

The Wave Unit contains Datawell’s accurate and well-proven stabilized platform sensor,
enabling wave height measurements by a single accelerometer. For the wave direction, direct
pitch and roll measurements are performed needing no integration. This, in combination with
horizontal accelerometers and a compass, forms the complete sensor unit which is the heart of
the Wave Unit.

The Wave Unit is meant to be integrated as a complete sensor package in oceanographic and
meteorological buoys.

The Wave Unit is equipped with an RS-232 interface and a power converter. Both the power
converter and the RS-232 interface are galvanically isolated for easy integration and overall
robustness. The power converter is suitable to accept a wide input voltage range from 10V up to
30V DC. The data format of the Wave Unit is compatible with the format as sent out by a
DWR-MkIII and can be used with the Waves4 software package and/or libdatawell
library. Alternatively, the data can be received, interpreted and forwarded by an embedded
system.

The Wave Unit is a highly sophisticated piece of equipment which hardly requires any attention.
For continuous reliable operation some maintenance is required however at low frequency
intervals. Chapter 2 Maintenance covers this topic.

In Chapter 3 Trouble Shooting several suggestions are made to tackle possible problems or even
carry out some small repairs.

During the operational life of your equipment calibration drift, aging or incidents could make it
necessary to send (part of) the equipment back to Datawell Service department. To serve you
best it is important to know exactly which parts fail and need to be returned. Please contact our
Service department prior to returning the equipment, stating serial number and complaint.
Chapter 4 Repair tells you where to locate serial numbers, how to contact Datawell Service
department and where to send parts.

This manual describes the operation of the following configuration:

 Wave Unit with stabilized platform accelerometer-based wave motion sensor
 Supply: 10 - 30 V DC, power consumption 400 mW max; reverse polarity and ESD

protected

 Stainless Steel housing
 Size (approximately): diameter 410 mm, height 560 mm
 Weight (approximately): 36 kg

Do not expose your Wave unit to sea water, install in a water tight compartment.

Also keep away any magnetic parts, since they will interfere with the magnetic compass
measurements and affect the measured wave direction

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2 Maintenance

During the operational life of your Wave Unit it will require some maintenance even though it
may function without error. We recommend to inspect the Wave Unit on every possible
occasion in order to prevent possible malfunctioning.

This chapter indicates which parts need servicing and when. Rather than extensively describing
the full maintenance procedure, this chapter gives a short summary. Please refer to the
description of the respective part in Chapter 5 Reference for the actual maintenance procedure.

2.1 Consumables

2.1.1 Bags of drying agent

In a hermetically sealed Wave Unit the bags with drying agent will protect the Wave Unit’s
electronics from taking up any possible moisture. In case the drying agent gets saturated it needs
to be dried in an oven, see subsection 5.6.6. Bags are located near the electronics in the lid
assembly and near the sensor electronics.

2.2 Inspection

2.2.1 Damage

We advise to inspect the Wave Unit for damage upon delivery.

2.2.2 Opening the Wave Unit and sealing rings

For reasons of importance it is noted in the beginning of the paragraph that before the lid is
opened, it should be rinsed with fresh water to avoid migration of salt and dirt into screw holes,
sealing ring grooves or the Wave Unit interior.

Remove dirt from the circular grooves of the housing flange and inspect the rubber sealing rings
for cuts. Clean grooves and intact sealing rings are essential for water tightness.

To open the lid refer to subsection 5.2.6.

2.3 Service

2.3.1 The Wave Unit’s wave motion sensor

The stabilized platform vertical accelerometer consists of a fluid-filled sphere. Over the years
the fluid evaporates through the Perspex sphere. Check the fluid level at least once every three
years. Experience showed that a small refill is required every three years. Section 5.3 will
explain where to check and how to refill.

As long as the sphere is correctly filled, the motion sensor is a robust sensor with nearly
perfectly buoyant invulnerable mechanics in the fluid. However, with insufficient fluid inside
the sphere, the mechanics in the fluid will no longer remain perfectly suspended and ultimately
will collapse under its own load. For a long life of your wave motion sensor carefully maintain
the sensor fluid level.

When in doubt, several tests in section 5.3 describe how to roughly verify the correct
functioning of your motion sensors.

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3 Trouble Shooting

This chapter will deal with minor problems that may occur and can be traced and solved by
yourself.

3.1 Wave Unit diagnosis

The Wave Unit has been provided with a processor board, which processes the digital signals to
the serial communication channel. This channel is available for host access. For the processor
board is a common part in most products of Datawell’s product range, it has some redundant
circuitry when using it in this Wave Unit application.

3.2 The Wave Unit motion sensors

The stabilized platform motion sensor is a very delicate instrument that can only be repaired by
skilled persons. In this section the symptoms of malfunction will be described, but faults are
almost impossible to repair for a layman.

3.2.1 Stabilized platform and accelerometer

The strength of the Datawell stabilized platform is that the heave is only determined by the
vertical accelerometer sensor. This implies that an erratic heave directly points at the vertical
accelerometer. Apart from the heave also the offset of the vertical accelerometer in the system
file, subsection 5.5.2.3, can be inspected. Possible causes are damaged suspension or internal
wires, moisture on the electronics, or low battery voltage.

Platform instability typically produces long period oscillations (20-25 s) of significant
amplitude (on the order of a meter) in the horizontal displacements. A faulty inclination angle
supports this. Likely causes are turbulence in the fluid or a sudden temperature change. Too fast
rotations may also cause turbulence. These disturbances will disappear within 24 hours. It
should be noted that pitch and roll errors can produce similar symptoms.

3.2.2 Magnetic compass
Inclination is the angle the local earth magnetic field makes with the local earth surface. A
measured inclination angle which matches the true local inclination within 1.5º indicates that (1)
the compass is functioning well, and (2) the offset angle of the platform is not too large. Local
inclination may be found on the web, e.g. visit www.ngdc.noaa.gov/seg/geomag/magfield.shtml.

Orientation is the angle between the reference axis of the Wave Unit and the magnetic north
direction. It does not depend on any tilt. The V-shaped groove indicates the reference axis.
Orientation may be easily verified with help of a hand held magnetic compass or the known
local north.

Furthermore, a plot of the inclination as function of the orientation can be made. The inclination
should remain constant for different orientation angles. A dependency of inclination on buoy
orientation can be caused by a platform offset angle or by an offset of the fluxgate compass.