Geokon 4422, Instruction Manual

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12
5. TROUBLESHOOTING
Maintenance and troubleshooting of monument crackmeters is confined to periodic checks of
cable connections and maintenance of terminals. Once installed, the crackmeters are usually
inaccessible and remedial action is limited.
Gages should not be opened in the field. Should
difficulties arise, consult the following list of problems and possible solutions. Return any faulty
gages to the factory. For additional troubleshooting and support, contact Geokon.
Symptom: Thermistor resistance is too high

It is likely that there is 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

It is likely that there is 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 crackmeter. There is no remedial action.
Symptom: Instrument 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 crackmeter shaft positioned outside the specified range (either extension or retraction)
of the instrument? Note that when the transducer shaft is fully retracted with the alignment
pin inside the alignment slot the readings will likely be unstable because the vibrating wire is
under-tensioned.

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 whether using a portable readout or
datalogger. Connect the shield drain wire to the readout using the blue clip. (Green for the
GK-401.)

Does the readout work with another gage? If not, it may have a low battery or possibly be
malfunctioning.
Symptom: Instrument Fails to Read

Is the cable cut or crushed? Check the resistance of the cable by connecting an ohmmeter to
the gage leads. Table 4 shows the expected resistance for the various wire combinations;
Table 5 is provided for the user to fill in the actual resistance found. Cable resistance is
approximately 14.74
Ω
per 1000' of 22 AWG wire. Multiply this factor by two to account for
both directions. If the resistance is very high or infinite (megohms), the cable is probably
broken or cut. If the resistance is very low (
<
20
Ω
), the gage conductors may be shorted. If a
cut or a short is located in the cable, splice according to the instructions in Section 2.4.

Does the readout or datalogger work with another gage? If not, it may have a low battery or
possibly be malfunctioning.