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12.28.1 Check the sensor coils
Checking the sensor coils can identify electrical shorts.
Restriction
This procedure applies only to 9-wire remote-mount transmitters and remote transmitters with
remote core processors..
Procedure
1. Disconnect power to the transmitter.
CAUTION!
If the transmitter is in a hazardous area, wait 5 minutes before continuing.
2. Remove the end-cap from the core processor housing.
3. Unplug the terminal blocks from the terminal board on the core processor.
4. 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 12-12 for a list of
the coils. Record the values.
Coils and test terminal pairsTable 12-12:
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 T-Series Yellow to orange
Fixed resistor (see note) CMF400 Yellow to orange
Note
The CMF400 fixed resistor applies only to certain specific CMF400 releases. Contact Micro
Motion 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 coil resistance tests at the sensor junction box
to eliminate the possibility of faulty cable. The readings for each coil pair should
match at both ends.
5.
Test the terminals in the sensor junction box for shorts to case.
Troubleshooting
242 Micro Motion
®
Model 2700 Transmitters with Analog Outputs