Geokon 6300 Instruction Manual

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Instruction Manual

Model 6300

Vibrating Wire In-Place Inclinometer

No part of this instruction manual may be reproduced, by any means, without the written consent of Geokon®.

The information contained herein is believed to be accurate and reliable. However, Geokon

omissions or misinterpretation. The information herein is subject to change without notification.

(Doc Rev Q, 05/01/19)

assumes no responsibility for errors,

Warranty Statement

Geokon warrants its products to be free of defects in materials and workmanship, under normal use and service for a period of 13 months from date of purchase. If the unit should malfunction, it must be returned to the factory for evaluation, freight prepaid. Upon examination by Geokon, if the unit is found to be defective, it will be repaired or replaced at no charge. However, the WARRANTY is VOID if the unit shows evidence of having been tampered with or shows evidence of being damaged as a result of excessive corrosion or current, heat, moisture or vibration, improper specification, misapplication, misuse or other operating conditions outside of Geokon's control. Components which wear or which are damaged by misuse are not warranted. This includes fuses and batteries.

Geokon manufactures scientific instruments whose misuse is potentially dangerous. The instruments are intended to be installed and used only by qualified personnel. There are no warranties except as stated herein. There are no other warranties, expressed or implied, including but not limited to the implied warranties of merchantability and of fitness for a particular purpose. Geokon is not responsible for any damages or losses caused to other equipment, whether direct, indirect, incidental, special or consequential which the purchaser may experience as a result of the installation or use of the product. The buyer's sole remedy for any breach of this agreement by Geokon or any breach of any warranty by Geokon shall not exceed the purchase price paid by the purchaser to Geokon for the unit or units, or equipment directly affected by such breach. Under no circumstances will Geokon reimburse the claimant for loss incurred in removing and/or reinstalling equipment.

Every precaution for accuracy has been taken in the preparation of manuals and/or software, however, Geokon neither assumes responsibility for any omissions or errors that may appear nor assumes liability for any damages or losses that result from the use of the products in accordance with the information contained in the manual or software.

TABLE of CONTENTS

1. INTRODUCTION ................................................................................................................................................... 1

1.1 TILT SENSOR CONSTRUCTION .............................................................................................................................. 2

2. INSTALLATION .................................................................................................................................................... 3

2.1 PRELIMINARY TESTS............................................................................................................................................ 3

2.2 MODEL 6300 ASSEMBLY AND INSTALLATION ..................................................................................................... 3

2.2.1 Uniaxial System .......................................................................................................................................... 4

2.2.2 Biaxial System ............................................................................................................................................. 5

2.3 FLUID DAMPING .................................................................................................................................................. 7

2.4 SPLICING AND JUNCTION BOXES.......................................................................................................................... 7

3. TAKING READINGS ............................................................................................................................................. 8

3.1 GK-404 READOUT BOX ....................................................................................................................................... 8

3.1.1 Operating the GK-404 ................................................................................................................................ 8

3.2 GK-405 READOUT BOX ....................................................................................................................................... 9

3.2.1 Connecting Sensors ..................................................................................................................................... 9

3.2.2 Operating the GK-405 ................................................................................................................................ 9

3.3 GK-403 READOUT BOX (OBSOLE TE MODEL) .................................................................................................... 10

3.3.1 Connecting Sensors ................................................................................................................................... 10

3.3.2 Operating the GK-403 .............................................................................................................................. 10

3.4 MEASURING TEMPERATURES ............................................................................................................................. 10

4. DATA REDUCTION ............................................................................................................................................ 11

4.1 INCLINATION CALCULATION.............................................................................................................................. 11

4.2 TEMPERATURE CORRECTION ............................................................................................................................. 11

4.3 DEFLECTION CALCULATION .............................................................................................................................. 12

4.4 ENVIRONMENTAL FACTORS ............................................................................................................................... 12

5. TROUBLESHOOTING ........................................................................................................................................ 13

APPENDIX A. SPECIFICATIONS ......................................................................................................................... 14

A.1 VIBRATING WIRE TILT SENSOR ........................................................................................................................ 14

A.2 THERMISTOR (SEE APPENDIX B ALSO) .............................................................................................................. 14

APPENDIX B. THERMISTOR TEMPERATURE DERIVATION ..................................................................... 15

APPENDIX C. EXCITATION AND READOUT PARAMETERS ...................................................................... 16

C.1 EXCITATION ...................................................................................................................................................... 16

C.2 EXCITATION FREQUENCY .................................................................................................................................. 16

C.3 OFFSET .............................................................................................................................................................. 16

APPENDIX D. ADDRESSABLE SYSTEMS .......................................................................................................... 17

APPENDIX E. TYPICAL CALIBRATION REPORT .......................................................................................... 18

FIGURES

IGURE 1 - MODEL 6300 TILT SENSOR ASSEMBLY ........................................................................................................ 1

FIGURE 2 - MODEL 6300 TILT SENSOR .......................................................................................................................... 2

FIGURE 3 - TYPICAL INSTALLATION .............................................................................................................................. 3

FIGURE 4 - BOTTOM WHEEL ASSEMBLY WITH SAFETY CABLE ...................................................................................... 4

FIGURE 5 - BIAXIAL SENSOR ASSEMBLY ........................................................................................................................ 5

FIGURE 6 - BIAXIAL SENSOR ORIENTATION ................................................................................................................... 5

FIGURE 7 - TOP SUSPENSION .......................................................................................................................................... 6

FIGURE 8 - LEMO CONNECTOR TO GK-404 ................................................................................................................... 8

FIGURE 9 - LIVE READINGS – RAW READINGS............................................................................................................... 9

FIGURE 10 - DEFLECTION INTERVALS ...........................................................................................................................12

FIGURE 11 - SAMPLE MODEL 6300 CALIBRATION REPORT ...........................................................................................18

TABLES

ABLE 1 - MODEL 6300 TILT SENSOR SPECIFICATIONS ................................................................................................14

TABLE 2 - THERMISTOR RESISTANCE VERSUS TEMPERATURE .....................................................................................15

EQUATIONS

EQUATION 1 - CALCULATION OF TILT (LINEAR) ...........................................................................................................11

EQUATION 2 - CALCULATION OF TILT (POLYNOMIAL)..................................................................................................11

EQUATION 3 - TEMPERATURE CORRECTION .................................................................................................................11

EQUATION 4 - HORIZONTAL DISPLACEMENT CALCULATION ........................................................................................12

EQUATION 5 - RESISTANCE TO TEMPERATURE .............................................................................................................15

1. INTRODUCTION

Plan View

Sensor Housing

Stationary Wheel

Spring Tensioned Wheel

Connecting Tube

Inclinometer Casing

Instrument Cable

The Geokon Model 6300 Vibrating Wire In-Place Inclinometer system is designed for long-term monitoring of deformations in structures such as dams, embankments, foundation walls and the like. The basic principle is the utilization of tilt sensors to make accurate measurement of inclination, over segments, in boreholes drilled into the structure being studied. The continuous nature of the instrument allows for very precise measurement of changes in the borehole profile to be measured. The instrument is installed in standard grooved inclinometer casing (Figure 1).

Figure 1 - Model 6300 Tilt Sensor Assembly

1.1 Tilt Sensor Construction

The sensor comprises a pendulous mass which is supported by a vibrating wire strain gauge and an elastic hinge (Figure 2). The strain gauge senses the changes in force caused by rotation of the center of gravity of the mass. The mass and sensor are enclosed in a waterproof housing which includes components for connecting the sensor to wheel assemblies and/or other sensors. The wheel assemblies centralize the sensors and allow the assembly to be lowered into the casing. Swivel joints are included to prevent the wheel assemblies from running out of the casing grooves due to spiral problems. Stainless steel tubing is used to connect the transducer and wheel assemblies together, and the whole string is normally supported from the top of the casing. Biaxial systems use two transducers mounted at 90° to each other.

To prevent damage during shipment the tilt sensors are locked in place by means of a locking clamp screw. This slotted-head clamp screw must be removed and replaced by a Phillips-head seal screw, (provided in the zip-lock bag), to render the tiltmeter operative.

Figure 2 - Model 6300 Tilt Sensor

2. INSTALLATION

Top Support

Pr ot ect i ve C ap

Gag e C abl e

Incl inometer

Wheel A ssemb l y

Sensor A ssembl y

Gage Tubing

Bott om Cap

Cable Connector

Casi ng

2.1 Preliminary Tests

Prior to installation, the sensors need to be checked for proper operation. Each tilt sensor is supplied with a calibration report that shows the relationship between readout digits and inclination. The tilt sensor electrical leads (usually the red and black leads) are connected to a readout box (see Section 3 for readout instructions) and the current reading compared to the calibration readings. After backing-off the clamp screw three full turns, carefully position the sensor against a vertical surface and observe the reading. It will take a few seconds to come to equilibrium and the sensor must be held in a steady position. The readings should be within ±200 digits of the factory reading, re-tighten the clamp screw three turns.

Note: Vibrating wire tilt sensors are shock sensitive and

severe shocks can cause a permanent offset or even break the suspension. (The unit will not survive a two foot (0.5 m) drop onto a hard surface). When transporting the tiltmeter

tighten the locking clamp screw.

Checks of electrical continuity can also be made using an ohmmeter. Resistance between the gauge leads should be approximately 180 Ω, ±10 ohms. Remember to add cable resistance when checking (22 AWG stranded copper leads are approximately 14.7Ω/1000' or 48.5Ω/km, multiply by two for both directions). The resistance between the green and white leads varies with temperature. Compare the measured resistance and ambient temperature to the factors shown in Table 2 in Appendix B. The resistance between any conductor and the shield should exceed two megohm.

2.2 Model 6300 Assembly and Installation

1) Connect the safety cable to the bottom wheel assembly. (See Figure 3.) This is strongly recommended. Not only can it be used to retrieve the assembly in the event that one of the joints breaks loose, but it is also very useful in lowering the assembly into the casing. The alternative is to hold the tube sections with vice-grips at the top of the casing.

Figure 3 - Typical Installation

The bottom anchor is labeled and has no Universal joint, just the swivel. The safety cable has a loop at its bottom end which fits over the long bolt used to hold the bottom anchor to the first tube section. This is shown in Figure 3. The cable eyebolt is trapped between two nuts.

Figure 4 - Bottom Wheel Assembly with Safety Cable

2) Connect the first length of gauge tubing to the bottom wheel assembly. The length of tube is shown in the table supplied with this manual. (In some cases, two tubes are joined together by a special union.) Use the 10-32 screws and nuts, and a thread locking cement to make this joint.

3) The next step is to attach the uniaxial or biaxial sensor assembly.

2.2.1 Uniaxial System

The uniaxial sensor is delivered unattached to its wheel assembly and should be attached using the two 10-32 nuts and cap screws supplied. The tongue of the sensor fits inside the slot of the wheel assembly with the orientation set such that the A+ direction marked on the sensor is aligned on the same side as the fixed wheel on the wheel assembly. Tilts in the positive direction yield increasing readings in digits.

Vibrating wire tilt sensors are shipped with a clamp screw holding the internal pendulum mechanism so that it is not damaged in shipment. A label is attached to each sensor emphasizing the importance of removing the slotted-head clamp screw completely and replacing it with the Phillips-head seal screw taped to the sensor. (Extra seal screws are provided in a zip-lock bag along with other accessories in case some become lost). This is very important for the sensor to be able to respond to tilting and remain waterproof.

The sensor and wheel assembly is now attached to the first tube section using a single long 10-32 cap screw. (Use Loctite 222 on all threads.)

Fixed Wheel

Instrument Cable

A+

B+

Instrument Cable

2.2.2 Biaxial System

The biaxial sensors are delivered unattached to the wheel assembly and to each other. The upper sensor should be attached to the wheel assembly using the two 10-32 nuts and cap screws supplied. The tongue of the sensor fits inside the slot of the wheel assembly with the orientation set such that the A+ direction marked on the sensor is aligned on the same side as the fixed wheel on the wheel assembly. (Tilts in the positive direction yield increasing readings in digits).

The adaptor piece is now bolted to the bottom of the sensor using a single 10-32 cap screw and thread locking compound (Loctite 222).

Two short cap screws are used to attach the lower sensor via this adaptor with its positive direction (Marked A+ on the sensor body) at 90° clockwise from the upper sensor (in plan looking down the casing). This will be the B+ direction. See Figure 6.

Note that there is some clearance around the bolt holes which will allow for some manual alignment of the sensors (absolute alignment is not critical).

When the two sensors are connected, the lower one is joined to the previously prepared gauge tube. Vibrating wire tilt sensors are shipped with a clamp screw holding the

internal pendulum mechanism so that it is not damaged in shipment. A label is attached to each sensor emphasizing the importance of removing the slotted-head clamp screw completely and replacing it with the Phillips-head seal screw taped to the sensor. (Extra seal screws are provided in a zip-lock bag along with other accessories in case some become lost). This is very important for the sensor to be able to respond to tilting and remain waterproof.

Figure 5 - Biaxial sensor assembly

Figure 6 - Biaxial Sensor Orientation

This assembly is now lowered into the borehole, using the safety cable, with the upper assembly fixed wheel aligned in the so-called A+ direction. It is customary (and recommended) to point the A+ direction in the same direction as the anticipated movement, i.e., towards the excavation being monitored or down-slope in the case of slope stability applications. Be sure that the lower wheel assembly and swivel are also aligned this way.

While holding the assembly at the top of the casing, using either the safety cable or vice grips on the tubing, the next segment with sensors, wheels and swivel are attached and lowered in the same orientation. The system can become quite heavy and a clamp of some sort may need to be used to hold the rods in place while being assembled. The use of a winch to hold the safety cable can be a help. Note that the longer cables are on reels to facilitate handling. Something like two little saw horses (or even folding chairs) with a broom stick across them to act as an axle will allow the cable to spool off as needed and provide a storage point for the rest of the cable.

The cables from the lower sensors should be taped or tie-wrapped to the assembly at intervals to support them as the system is built up and lowered down the borehole.

Continue to add gauge tubing, sensors and wheel assemblies until the last sensor has been attached to the upper wheel assembly, which is pre-assembled to the top suspension (Figure 7). The Top suspension can then be lowered into position on the casing. It is important that the end of the casing be cut square to prevent any side pressure on the upper sensor wheel assembly.

Figure 7 - Top Suspension

After the sensor string has been lowered into position, the safety cable can be tied off around the top of the casing and the signal cables can be run to the readout location and terminated or otherwise fixed. Readings should be taken immediately after installation, but it is recommended that the system be allowed to stabilize for a few hours before recording zero conditions.

For IPI strings that are going to measure only across a subsurface zone of interest and will not reach the surface, the cross-piece of the top suspension is omitted and the IPI string is suspended at the proper depth by a length of aircraft cable, attached to the eyebolt, and tied off at the top of the casing.

2.3 Fluid Damping

The vibrating wire tilt sensor acts as a self-damping system when used in vibration free environments. When external ground or structural vibrations exceed a certain threshold, the pendulous mass will continue to "dither" and stable readings may not be possible. In such cases, additional damping can be achieved by adding a viscous damping fluid to a small reservoir contained in the sensor. A thin, wide "paddle" is connected to the mass and when the fluid is added the pendulum is damped by the action of the paddle in the damping fluid.

Most in-place installations will not require this fluid. However, if the instrument gives unstable outputs, or it is known that the structure is constantly vibrating, the fluid can be added. The fluid is a high-viscosity silicone oil which must be injected into the sensor with a syringe.

The sensor must be held upright during the injection of the fluid and at all times following the injection. This makes it necessary to perform this operation in the field. The following applies for a typical in-place installation.

1) After connecting the sensor to the gauge tubing already in the casing, and after removal of

the clamping screw, use the syringe applied, first pull the piston from the syringe and squeeze the silicone from the tube into the syringe. Replace the piston and start the silicone oil out of the "needle" end.

2) Now, inject 2.00 cc into the hole in the sensor. Immediately following this operation, the seal

screw should be replaced in the sensor.

3) The sensor may now be lowered into the casing.

2.4 Splicing and Junction Boxes

Because the vibrating wire output signal is a frequency rather than current or voltage, variations in cable resistance have little effect on gauge readings and, therefore, splicing of cables has little effect and, in some case, may be beneficial. For example, if multiple sensors are installed in a borehole, and the distance from the borehole to the terminal box or datalogger is great, a splice could be made to connect the individual cables to a single multi-conductor cable. This multiconductor cable would then be run to the readout station. For such installations it is recommended that the transducer be supplied with enough cable to reach the top of the casing plus enough extra to make splicing possible.

The cable used for making splices should be a high-quality twisted pair type with 100% shielding (with integral shield drain wire). When splicing, it is very important that the shield drain wires be spliced together! Splice kits recommended by Geokon incorporate casts placed around the splice then filled with epoxy to waterproof the connections. When properly made, this type of splice is equal or superior to the cable itself in strength and electrical properties. Contact Geokon for splicing materials and additional cable splicing instructions.

Junction boxes and terminal boxes are available from Geokon for all types of applications. In addition, portable readout equipment and datalogging hardware are available. Contact Geokon for specific application information.

3. TAKING READINGS

3.1 GK-404 Readout Box

The Model GK-404 Vibrating Wire Readout is a portable, low-power, handheld unit that can run continuously for more than 20 hours on two AA batteries. It is designed for the readout of all Geokon vibrating wire gauges and transducers; and is capable of displaying the reading in either digits, frequency (Hz), period (µs), or microstrain (µε). The GK-404 also displays the temperature of the transducer (embedded thermistor) with a resolution of 0.1 °C.

3.1.1 Operating the GK-404

Before use, attach the flying leads to the GK-404 by aligning the red circle on the silver “Lemo” connector of the flying leads with the red line on the top of the GK-404 (Figure

8). Insert the Lemo connector into the GK-404 until it locks into place.

Figure 8 - Lemo Connector to GK-404

Connect each of the clips on the leads to the matching colors of the sensor conductors, with blue representing the shield (bare).

To turn the GK-404 on, press the “ON/OFF” button on the front panel of the unit. The initial startup screen will be displayed. After approximately one second, the GK-404 will start taking readings and display them based on the settings of the POS and MODE buttons.

The unit display (from left to right) is as follows:

• The current Position: Set by the POS button. Displayed as a letter A through F.

• The current Reading: Set by the MODE button. Displayed as a numeric value

followed by the unit of measure.

• Temperature reading of the attached gauge in degrees Celsius.

Use the POS button to select position B and the MODE button to select Dg (digits). (Other functions can be selected as described in the GK-404 Manual.)

The GK-404 will continue to take measurements and display readings until the unit is turned off, either manually, or if enabled, by the Auto-Off timer. If the no reading displays or the reading is unstable, see Section 5 for troubleshooting suggestions.

For further information, please see the GK-404 manual.

3.2 GK-405 Readout Box

The GK-405 Vibrating Wire Readout is made up of two components: The Readout Unit, consisting of a Windows Mobile handheld PC running the GK-405 Vibrating Wire Readout Application; and the GK-405 Remote Module, which is housed in a weatherproof enclosure and connects to the vibrating wire gauge to be measured. The two components communicate wirelessly. The Readout Unit can operate from the cradle of the Remote Module, or, if more convenient, can be removed and operated up to 20 meters from the Remote Module.

3.2.1 Connecting Sensors

Connecting sensors with 10-pin connectors:

Align the grooves on the sensor connector (male), with the appropriate connector on the readout (female connector labeled senor or load cell). Push the connector into place, and then twist the outer ring of the male connector until it locks into place.

Connecting sensors with bare leads:

Attach the GK-403-2 flying leads to the bare leads of a Geokon vibrating wire sensor by connecting each of the clips on the leads to the matching colors of the sensor conductors, with blue representing the shield (bare).

3.2.2 Operating the GK-405

Press the button labeled “POWER ON”. A blue light will begin blinking, signifying that the Remote Module is waiting to connect to the handheld unit. Launch the GK-405 VWRA program by tapping on “Start” from the handheld PC’s main window, then “Programs” then the GK-405 VWRA icon. After a few seconds, the blue light on the Remote Module should stop flashing and remain lit. The Live Readings Window will be displayed on the handheld PC. Choose display mode “B”. Figure 9 shows a typical vibrating wire output in digits and thermistor output in degrees Celsius. If no reading displays or the reading is unstable, see Section 5 for troubleshooting suggestions. For further information, consult the GK-405 Instruction Manual.

Figure 9 - Live Readings – Raw Readings

3.3 GK-403 Readout Box (Obsolete Model)

The GK-403 can store gauge readings and apply calibration factors to convert readings to engineering units. The following instructions explain taking gauge measurements using Mode “B”. Consult the GK-403 Instruction Manual for additional information.

3.3.1 Connecting Sensors

Connecting sensors with 10-pin connectors:

Connecting Sensors with Bare Leads:

3.3.2 Operating the GK-403

1) Turn the display selector to position “B”.

2) Turn the unit on.

3) The readout will display the vibrating wire output in digits. The last digit may change

one or two digits while reading.

4) The thermistor reading will be displayed above the gauge reading in degrees

centigrade.

5) Press the “Store” button to record the value displayed.

If the no reading displays or the reading is unstable, see Section 5 for troubleshooting suggestions. The unit will turn off automatically after approximately two minutes to conserve power.

3.4 Measuring Temperatures

Each Vibrating tilt sensor is equipped with a thermistor for reading temperature. The thermistor gives a varying resistance output as the temperature changes. Geokon readout boxes will read the thermistor and display temperature in °C automatically. To read the thermistor using an ohmmeter, complete the following:

1) Connect the ohmmeter to the two thermistor leads coming from the instrument. (Usually white and green.) Since the resistance changes with temperature are large, the effect of cable resistance is usually insignificant.

2) Look up the temperature for the measured resistance in Table 2 in Appendix B.

4. DATA REDUCTION

4.1 Inclination Calculation

Inclinations are measured in digits on Position B on the Geokon readout. The output of the VW tilt sensor is proportional to the sine of the angle of tilt. For small angles θ and sinθ are the same, so the relationship between output digits and the amount of tilting, (change of the angle of inclination), ∆θ, is given by the equation:

∆θ = ∆sinθ = (R1 − R0) G degrees tilt

Equation 1 - Calculation of Tilt (Linear)

Where; R1 is the current reading in digits

Ro is the initial reading in digits G is the Linear Gauge Factor in degrees tilt/digit given on the calibration report supplied with the

sensor. (A sample calibration report is shown in Appendix E.)

The linear equation works very well for inclinations of less than four degrees. More than this and the linearity errors start to increase beyond 0.5% FS. The error incurred by using the linear equation is shown on the calibration chart.

For better accuracy at larger inclinations use the polynomial equation: This uses a second order curve to approximate the sine curve.

θ = R2A + RB + C degrees tilt

Equation 2 - Calculation of Tilt (Polynomial)

Where A, B and C are the coefficients supplied on the calibration report. Calculate θ1 by substituting R = R1 in the formula and then calculate θ0 by substituting R = R0 then subtract to find the difference ∆θ = (θ1 - θ0).

4.2 Temperature Correction

The Model 6350 Tiltmeter has a slight temperature sensitivity on the order of -0.5 digit per °C rise, i.e. the reading falls by 0.5 digits for every one °C rise of temperature. The temperature correction is:

+0.5G(T1-T0) degrees tilt

Equation 3 - Temperature Correction

Normally, corrections are not applied for this small effect because the structure being monitored usually is affected to a much greater degree. An important point to note, also, is that sudden changes in temperature will cause both the structure and the Tiltmeter to undergo transitory physical changes that will show up in the readings. The gauge temperature should always be recorded for comparison, and efforts should be made to obtain readings when the instrument and structure are at thermal equilibrium. The best time for this tends to be in the late evening or early morning hours.

4.3 Deflection Calculation

Now, the change in reading must be converted to a lateral deflection. The lateral deflection is defined as Lsin∆θ where L is the gauge length between pivot points and ∆θ is the change in inclination (corrected for temperature) determined from Equation 3.

The length L1, L2, L3,…. etc., can be calculated by adding 311 mm, (uniaxial systems) or 524 mm, (biaxial system), to the individual lengths of tubing. This will give the correct distance between pivot points.

The horizontal displacement profile can be constructed by using the cumulative sum of the displacement starting with the bottom segment. Subsequent readings over time will reveal changes in deflection, possible shear zones, etc. For example, referring to Figure 10 and Equation 4.

D1 = L1 ∆sinθ1

D2 = L1 ∆sinθ1 + L2 ∆sinθ

D3 = L1 ∆sinθ1 + L2 ∆sinθ2 + L3 ∆sinθ3

D4 = L1 ∆sinθ1 + L2 ∆sinθ2 + L3 ∆sinθ3 + L4 ∆sinθ4

D5 = L1 ∆sinθ1 + L2 ∆sinθ2 + L3 ∆sinθ3 + L4 ∆sinθ4 +L5 ∆sinθ

Where, for small angles:

∆sinθ = (R1 − R0) G

Equation 4 - Horizontal Displacement Calculation

Although the system is designed for use with continuous segments and pivots, the sensors can be installed without interconnecting tubing in standard, round tubing or pipe using special friction anchoring. In those systems, the assumption is made that the measured deflection occurs over the segment length and that L is the distance between sensors.

4.4 Environmental Factors

Since the purpose of the inclinometer installation is to monitor site conditions, factors that may affect these conditions should be observed and recorded. Seemingly minor effects may have a real influence on the behavior of the structure being monitored and may give an early indication of potential problems. Some of these factors include, but are not limited to: blasting, rainfall, tidal or reservoir levels, excavation and fill levels and sequences, traffic, temperature and barometric changes, changes in personnel, nearby construction activities, seasonal changes, etc.

Figure 10 -

Deflection Intervals

5. TROUBLESHOOTING

Maintenance and troubleshooting of the vibrating wire tilt sensors used in the Model 6300 Inclinometer are is confined to periodic checks of cable connections. The sensors are sealed and there are no user-serviceable parts.

Consult the following list of problems and possible solutions should difficulties arise. Consult the factory for additional troubleshooting help.

Symptom: Tilt Sensor Readings are Unstable:

 Is the readout box position set correctly? If using a datalogger to record readings

automatically are the swept frequency excitation settings correct?

 Is there a source of electrical noise nearby? Most probable sources of electrical noise are

motors, generators and antennas. Make sure the shield drain wire is connected to ground whether using a portable readout or datalogger. If using the GK-403, GK-404, or GK-405 connect the clip with the blue boot to the shield drain wire. (Green for the GK-401)

 Does the readout work with another tilt sensor? If not, the readout may have a low battery or

be malfunctioning.

Symptom: Tilt Sensor Fails to Read:

 Is the cable cut or crushed? This can be checked with an ohmmeter. Nominal resistance

between the two gauge leads (usually red and black leads) is 180Ω, ±10Ω. Remember to add cable resistance when checking (22 AWG stranded copper leads are approximately

14.7Ω/1000' or 48.5Ω/km, multiply by two for both directions). If the resistance reads infinite, or very high (megohms), a cut wire must be suspected. If the resistance reads very low (<20Ω) a short in the cable is likely.

 Does the readout or datalogger work with another tilt sensor? If not, the readout or datalogger

may be malfunctioning.

Symptom: Thermistor resistance is too high:

 Is there an open circuit? Check all connections, terminals and plugs. If a cut is located in the

cable, splice according to instructions in Section 2.4.

Symptom: Thermistor resistance is too low:

 Is there a short? Check all connections, terminals and plugs. If a short is located in the cable,

splice according to instructions in Section 2.4.

 Water may have penetrated the interior of the tilt sensor. There is no remedial action.

Model:

6300

Range:¹

±10°

Resolution:²

8 arc seconds

Accuracy:³

±8 arc seconds

Linearity:4

±0.3% FSR

Thermal Zero Shift:

±4 arc seconds/°C

Operating

Temperature

-40 to +80° C

-40 to 175° F

Operating Frequency:

1400-3500 Hz

Coil Resistance:

180 Ω

Diameter:

1.250", 32 mm

Length:

7.375", 187 mm

Weight:

1.5 lbs., 0.7 kg.

Materials:

304 Stainless Steel

Electrical Cable:

Two twisted pair (four conductor) 22 AWG

Foil shield, PVC jacket, nominal OD=6.3 mm (0.250")

APPENDIX A. SPECIFICATIONS

A.1 Vibrating Wire Tilt Sensor

Table 1 - Model 6300 Tilt Sensor Specifications

Notes: ¹ Consult the factory for other ranges. ² Depends on readout equipment. With averaging techniques, it is possible to achieve one arc second ³ Derived using 2nd order polynomial.

The output from the sensor is proportional to the sine of the angle of tilt

A.2 Thermistor (see Appendix B also)

Range: -80 to +150 °C Accuracy: ±0.5 °C

APPENDIX B. THERMISTOR TEMPERATURE DERIVATION

Ohms

Temp

Ohms

Temp

Ohms

Temp

Ohms

Temp

Ohms

Temp

201.1K

-50

16.60K

-10

2417

+30

525.4

+70

153.2

+110

187.3K

-49

15.72K

-9

2317

507.8

149.0

111

174.5K

-48

14.90K

-8

2221

490.9

145.0

112

162.7K

-47

14.12K

-7

2130

474.7

141.1

113

151.7K

-46

13.39K

-6

2042

459.0

137.2

114

141.6K

-45

12.70K

-5

1959

444.0

133.6

115

132.2K

-44

12.05K

-4

1880

429.5

130.0

116

123.5K

-43

11.44K

-3

1805

415.6

126.5

117

115.4K

-42

10.86K

-2

1733

402.2

123.2

118

107.9K

-41

10.31K

-1

1664

389.3

119.9

119

101.0K

-40

9796 0 1598

376.9

116.8

120

94.48K

-39

9310

1535

364.9

113.8

121

88.46K

-38

8851 2 1475

353.4

110.8

122

82.87K

-37

8417 3 1418

342.2

107.9

123

77.66K

-36

8006 4 1363

331.5

105.2

124

72.81K

-35

7618 5 1310

321.2

102.5

125

68.30K

-34

7252 6 1260

311.3

99.9

126

64.09K

-33

6905 7 1212

301.7

97.3

127

60.17K

-32

6576 8 1167

292.4

94.9

128

56.51K

-31

6265 9 1123

283.5

92.5

129

53.10K

-30

5971

1081

274.9

90.2

130

49.91K

-29

5692

1040

266.6

87.9

131

46.94K

-28

5427

1002

258.6

85.7

132

44.16K

-27

5177

965.0

250.9

83.6

133

41.56K

-26

4939

929.6

243.4

81.6

134

39.13K

-25

4714

895.8

236.2

79.6

135

36.86K

-24

4500

863.3

229.3

77.6

136

34.73K

-23

4297

832.2

222.6

75.8

137

32.74K

-22

4105

802.3

216.1

73.9

138

30.87K

-21

3922

773.7

209.8

72.2

139

29.13K

-20

3748

746.3

203.8

100

70.4

140

27.49K

-19

3583

719.9

197.9

101

68.8

141

25.95K

-18

3426

694.7

192.2

102

67.1

142

24.51K

-17

3277

670.4

186.8

103

65.5

143

23.16K

-16

3135

647.1

181.5

104

64.0

144

21.89K

-15

3000

624.7

176.4

105

62.5

145

20.70K

-14

2872

603.3

171.4

106

61.1

146

19.58K

-13

2750

582.6

166.7

107

59.6

147

18.52K

-12

2633

562.8

162.0

108

58.3

148

17.53K

-11

2523

543.7

157.6

109

56.8

149

Table 2 - Thermistor Resistance Versus Temperature

55.6

150

Thermistor Type: YSI 44005, Dale #1C3001-B3, Alpha #13A3001-B3 Resistance to Temperature Equation:

A+B(LnR)+C(LnR)

Equation 5 - Resistance to Temperature

Where;

T = Temperature in °C. LnR = Natural Log of Thermistor Resistance

A = 1.4051 × 10-3

B = 2.369 × 10-4

C = 1.019 × 10-7

Note: Coefficients calculated over the −50 to +150° C. span.

-273.15 °C

APPENDIX C. EXCITATION AND READOUT PARAMETERS

The Micro-10 Datalogger which uses the Campbell Scientific Measurement and Control Module can be used to continuously monitor the Model 6300.

The following parameters are recommended:

C.1 Excitation

The 2.5-volt excitation directly off the wiring panel is ideal for these sensors. The 5-volt supply from the AVW-1 and AVW-4 modules is also usable, but the 12-volt excitation should be avoided as it tends to overdrive the sensor.

C.2 Excitation Frequency

The starting and ending frequencies of the excitation sweep should be kept in a relatively narrow band for these sensors to maximize the stability and resolution of the output.

The frequency band for the full range is shown on the calibration reports.

The frequencies can be determined from these. The highest and lowest frequencies shown can be used to determine the sweep parameters. After initial readings are obtained, parameters should be set to 200 Hz below the resonant frequency and 1-200 Hz above.

C.3 Offset

To maximize the five-digit, high resolution output, the offset parameter can be used to remove the zero offset of the sensor.

In other words, if the installed reading is 4,300, the offset parameter could be set at -4300 which would theoretically change the resolution from 0.1 digit to 0.0001 digit.

For assistance in programming these parameters contact Geokon, Inc.

Appendix D. Addressable Systems

The Addressable system allows all the borehole sensors to be connected to a single cable rather than have a separate cable for each sensor. The sensors are supplied in a string connected together by pre-determined lengths of cables specified by the customer.

The string of sensor is installed in a manner to that described in Section 2.

The cable is connected, via a 15-pin connector, to a special Geokon Model 8021-1X datalogger modified, by the addition of a Model 8031 Distributed Multiplexer, specifically for use with the addressable system

APPENDIX E. TYPICAL CALIBRATION REPORT

Figure 11 - Sample Model 6300 Calibration Report

Geokon 6300 Instruction Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

1. INTRODUCTION

1.1 Tilt Sensor Construction

2. INSTALLATION

2.1 Preliminary Tests

2.2 Model 6300 Assembly and Installation

2.2.1 Uniaxial System

2.2.2 Biaxial System

2.3 Fluid Damping

2.4 Splicing and Junction Boxes

3. TAKING READINGS

3.1 GK-404 Readout Box

3.1.1 Operating the GK-404

3.2 GK-405 Readout Box

3.2.1 Connecting Sensors

3.2.2 Operating the GK-405

3.3 GK-403 Readout Box (Obsolete Model)

3.3.1 Connecting Sensors

3.3.2 Operating the GK-403

3.4 Measuring Temperatures

4. DATA REDUCTION

4.1 Inclination Calculation

4.2 Temperature Correction

4.3 Deflection Calculation

4.4 Environmental Factors

5. TROUBLESHOOTING

APPENDIX A. SPECIFICATIONS

A.1 Vibrating Wire Tilt Sensor

A.2 Thermistor (see Appendix B also)

APPENDIX B. THERMISTOR TEMPERATURE DERIVATION

APPENDIX C. EXCITATION AND READOUT PARAMETERS

C.1 Excitation

C.2 Excitation Frequency

C.3 Offset

Appendix D. Addressable Systems

APPENDIX E. TYPICAL CALIBRATION REPORT