Maintenance and troubleshooting of embedment strain gauges is confined to periodic checks of cable connections and maintenance of terminals. Once installed, the gauges are usually inaccessible and remedial action is limited.
Should difficulties arise, consult the following list of problems and possible solutions.
Return faulty gauges to geokon. Gauges should not be disassembled in the field.
For additional troubleshooting and support, contact geokon.
Symptom: Thermistor resistance is too high
□There may be an open circuit. Check all connections, terminals, and plugs. If a cut is located in the cable, splice according to instructions in Section 4.1.
Symptom: Thermistor resistance is too low
□There may be a short. Check all connections, terminals, and plugs. If a short is located in the cable, splice according to instructions in Section 4.1.
□Water may have penetrated the interior of the transducer. There is no remedial action.
Symptom: Strain Gauge 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 the strain reading outside the specified compressive or tensile range of the instrument? The gauge may have become too slack or too tight; inspect the data to determine whether this is a possibility.
□Is there a source of electrical noise nearby? Likely candidates are generators, motors, arc welding equipment, high-voltage lines, etc. If possible, move the instrument cable away from power lines and electrical equipment or install electronic filtering.
□Make sure the shield drain wire is connected to ground.
□Does the readout or datalogger work with another gauge? If not, it may have a low battery or possibly be malfunctioning.
Symptom: Strain Gauge Fails to Read
□Is the cable cut or crushed? Check the resistance of the cable by connecting an ohmmeter to the sensor leads. Cable resistance is approximately 14.7Ω per 1000 ft (48.5Ω per km) of 22 AWG wire.
□If the resistance is very high or infinite, the cable is probably broken or cut. If the resistance is very low, the gauge conductors may be shorted. If a cut or a short is located in the cable, splice according to the instructions in Section 4.1.
□Does the readout or datalogger work with another gauge? If not, it may have a low battery or possibly be malfunctioning.
Refer to the expected resistance for the various wire combinations below.
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Vibrating Wire Sensor Lead Resistance Levels |
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Red/Black |
≅180Ω (≅50Ω for Models 4202 & 4200HT‑T, ≅120Ω for Model 4200HT) |
Any other wire combination will result in a measurement of infinite resistance.