Common Mode Rejection Measurement; Troubleshooting; Fault Indication #1 - GE Bently Nevada 86517 Operation Manual

4.2 Common Mode Rejection Measurement

The amount of noise that will appear at the output of the module is directly
related to the interface module's ability to reject common mode voltage at its
input. To assure that the module's noise floor remains in accordance with the
specification by which it was designed, the following common mode rejection
measurement is recommended every two years. If the interface module does not
perform within the limits outlined below, return the module to Bently Nevada in
Minden, Nevada for repair.
1. Connect terminals A and C together. Input 5 Vp-p (1.767 Vrms) @ 600 Hz
to terminal C. Verify output at "+ ACCEL" (TB1-6) is less than 60 mVrms.
2. Change frequency to 1000 Hz. Verify output at TB1-6 is less than 56
mVrms.

4.3 Troubleshooting

The following troubleshooting procedure will help
you interpret a fault indication and isolate faults
in an installed transducer
system. Before beginning make
sure the system has been
correctly.
When a malfunction occurs, locate the fault indication, check the probable
causes for the fault indication, and follow the procedure to isolate and correct the
problem.

4.3.1 Fault Indication #1:

The voltage between the -24Vdc and COM terminals is not within the range of -22
Vdc to -25 Vdc
(-16.0 Vdc to -25 Vdc with safety barriers).
Probable Cause:
Faulty wiring between the monitor and the interface module.
Faulty power supply.
Faulty interface module.
Isolation and Correction:
Disconnect the power and signal wiring from the interface module and
measure the voltage between the common wire and the supply voltage
wire. If the voltage remains outside the limits then there is a problem with
either the power supply or the power and common field wiring. If the
Section 4 - MAINTENANCE
CAUTION
Machine protection will be lost
during these procedures.
installed
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