15.32 Check for internal electrical problems
Shorts between sensor terminals or between the sensor terminals and the sensor case can cause the sensor to
stop working.
Possible cause Recommended action
Liquid or moisture inside the sensor case Contact customer support.
Internally shorted feedthrough Contact customer support.
Faulty cable Replace the cable.
15.32.1 Check the sensor coils
Checking the sensor coils can identify a cause for a no sensor response alert.
Restriction
This procedure applies only to 9-wire remote-mount transmitters.
Procedure
1. Disconnect power to the transmitter.
CAUTION
If the transmitter is in a hazardous area, wait 5 minutes before continuing.
2. Unplug the terminal blocks from the terminal board on the core processor.
3. Using a digital multimeter (DMM), check the pickoff coils by placing the DMM leads on the unplugged
terminal blocks for each terminal pair. See Table 15-5 for a list of the coils. Record the values.
Table 15-5: Coils and test terminal pairs
Coil Sensor model Terminal colors
Drive coil All Brown to red
Left pickoff coil (LPO) All Green to white
Right pickoff coil (RPO) All Blue to gray
Resistance temperature detector
(RTD)
All Yellow to violet
Lead length compensator (LLC) All except T-Series and CMF400 (see
note)
Yellow to orange
Composite RTD CMFS025-150 and T-Series Yellow to orange
Fixed resistor (see note) CMFS007, CMFS010, CMFS015,
CMF400, and F300
Yellow to orange
Note
The CMF400 fixed resistor applies only to certain specific CMF400 releases. Contact customer support
for more information.
There should be no open circuits, that is, no infinite resistance readings. The left pickoff and right
pickoff readings should be the same or very close (±5 Ω). If there are any unusual readings, repeat the
Troubleshooting Configuration and Use Manual
April 2019 MMI-20048166
202 Micro Motion 4200 Transmitters
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