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Procedure
1. Disconnect power to the transmitter.
CAUTION!
If the transmitter is in a hazardous area, wait 5 minutes before continuing.
2. Remove the transmitter housing cover.
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 10-12 for a list of
the coils. Record the values.
Coils and test terminal pairsTable 10-12:
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.
a. Leave the terminal blocks disconnected.
b. Remove the lid of the junction box.
c. Testing one terminal at a time, place a DMM lead on the terminal and the other
lead on the sensor case.
With the DMM set to its highest range, there should be infinite resistance on
each lead. If there is any resistance at all, there is a short to case.
Troubleshooting
Configuration and Use Manual 189