13
5. TROUBLESHOOTING
Maintenance and troubleshooting of embedment strain gages are confined to periodic
checks of cable connections and maintenance of terminals. Once installed, the gages are
usually inaccessible and remedial action is limited.
Consult the following list of problems and possible solutions should difficulties arise.
Consult the factory for additional troubleshooting help.
Symptom: Strain Gage 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 range (either compressive or tensile) of the
instrument?
Is there a source of electrical noise nearby? Most probable sources of electrical noise
are motors, generators and antennas. Move the equipment away from the installation or
install electronic filtering. Make sure the shield drain wire is connected to ground
whether using a portable readout or datalogger.
Does the readout work with another gage? If not, the readout may have a low battery or
be malfunctioning.
Symptom: Strain Gage Fails to Read
Is the cable cut or crushed? This can be checked with an ohmmeter. Nominal
resistance between the two gage leads (usually red and black leads) is 180
,
10
.
Remember to add cable resistance when checking (22 AWG stranded copper leads are
approximately 14.7
/1000' or 48.5
/km, multiply by 2 for both directions). If the
resistance reads infinite, or very high (megohms), a cut wire must be suspected. If the
resistance reads very low (
100
) a short in the cable is likely. Splicing kits and
instructions are available from the factory to repair broken or shorted cables. Consult
the factory for additional information.
Does the readout or datalogger work with another strain gage? If not, the readout or
datalogger may be malfunctioning.
