Fault Isolation And Correction - GE Bently Nevada 7200 Series Installation Manual

FAULT INDICATION
Voltage between Prox. COM
and V terminals not within
T
range of -17.5 to -26 Vdc.
Voltage between Prox.
OUTPUT and COM
terminals remains at zero
volts.
Voltage between Prox.
OUTPUT and COM
terminals remains at more
than zero and less than 1
volt.
Voltage between Prox.
OUTPUT and COM
terminals remains within a
few volts but is not identical
to the voltage between COM
and V terminals.
T
Voltage between Prox.
OUTPUT and COM
terminals remains identical
to voltage between COM
and V terminals.
T
Table 3-2. Fault Isolation and Correction
PROBABLE CAUSE
1. Faulty power source.
2. Faulty wiring between power
source and Proximitor.
1. Short circuit in field wiring or
instrument connected to Proximitor
OUTPUT terminal.
2. Faulty Proximitor.
1. Short circuit in probe.
2. Short circuit in probe cable.
NOTE: A gap of less than 10 mils
between the probe tip and observed
surface could cause an indication like
a short circuit.
1. Faulty Proximitor
2. Open circuit in probe. NOTE: A
gap between the probe tip and
observed surface that is too large for
the transducer to measure could cause
an indication similar to an open probe
circuit.
1. Short circuit in wiring between
Proximitor OUTPUT and V
T
terminals.
2. Faulty Proximitor.
ISOLATION AND CORRECTION
Disconnect output wiring from power source. Measure power source output
voltage. If not within range of -17.5 to -26 Vdc, replace the power source.
If power source output voltage is within range of
exists in wiring between power source and Proximitor or in the Proximitor.
Reconnect wiring at power supply and disconnect at Proximitor. If voltage
at wire terminals which connect to Proximitor is not correct, replace faulty
wiring. If voltage is correct, replace Proximitor.
Disconnect wiring from Proximitor OUTPUT terminal. Remeasure voltage
between Proximitor OUTPUT and COM terminals. If a voltage other than
zero is measured, replace field wiring or instrument that was connected to
Proximitor OUTPUT terminal. If voltage is zero, replace Proximitor.
Disconnect cable from Proximitor. Remeasure voltage between Proximitor
OUTPUT and COM terminals. If unchanged, replace Proximitor. If within
a few volts of the voltage between Proximitor COM and V
short circuit exists in probe cable. Clean probe cable connector with solvent
such as Freon. Reconnect probe lead to Proximitor. Remeasure voltage
between Proximitor OUTPUT and COM terminals. If still zero volts,
replace the probe.
Disconnect probe cable from the Proximitor. Using a small piece of wire,
short the center pin to the outer shell of the coaxial connector on the
Proximitor and remeasure the output voltage. If the voltage is not 0.6 to 0.8
volts, replace the Proximitor. If the voltage is between 0.6 and 0.8 volts, an
open circuit exists in the probe. Using the DMM set to the resistance
function, measure the outer conductor and the inner conductor of the probe.
Normal resistance of the probe measured center to outer is 3 to 9 ohms.
Replace faulty probe.
Remove wiring from Proximitor OUTPUT terminal. Remeasure voltage
between Proximitor OUTPUT and COM terminals. If voltage is less than
supply, a short circuit exists in wiring between Proximitor OUTPUT and V
terminals. If voltage is unchanged, replace Proximitor.
APPENDIX A
-17.5 to -26 Vdc, fault
terminals, a
T
T
15