Geokon 4425, Instruction Manual, Page: 21 / 27

15
5. TROUBLESHOOTING
Maintenance and troubleshooting of Geokon Vibrating Wire Convergence Meters are confined
to periodic checks of cable connections and maintenance of terminals. The Convergence Meters
contain no user serviceable components. However, consult the following list of problems and
possible solutions should difficulties arise. Consult the factory for additional troubleshooting
help.
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 2.5.
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 2.5.

Water may have penetrated the interior of the Convergence Meter. 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 transducer shaft of the Convergence Meter positioned outside the specified range of
the instrument? Note that when the transducer shaft is fully retracted with the alignment pin
inside the alignment slot (as shown in Figure 1) the readings will likely be unstable because the
transducer is now out of range.

Is there a source of electrical noise nearby? Most probable sources of electrical noise are
motors, generators, transformers, arc welders, and antennas. Make sure the shield drain wire is
connected to ground whether using a portable readout or datalogger. If using the GK-401
Readout connect the clip with the green boot to the bare shield drain wire of the pressure cell
cable. If using the GK-403 connect the clip with the blue boot to the shield drain wire.
Symptom: Instrument Fails to Read:

Is the cable cut or crushed? Check the resistance of the cable by connecting an ohmmeter
to the gauge leads. Table 7 on the following page shows the expected resistance for the various
wire combinations; Table 8 is provided to fill in the actual resistance found. Cable resistance is
approximately 14.7
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 gauge conductors may be shorted. If a cut or a short is located
in the cable, splice according to the instructions in Section 2.5.

Does the readout or datalogger work with another gauge? If not, it may have a low
battery or possibly be malfunctioning.