
Configuration and Use Manual
157
Troubleshooting
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12.27
Checking sensor coils and RTD
Problems with sensor coils can cause several alarms, including sensor failure and a variety of
out-of-range conditions. Testing the sensor coils involves testing the terminal pairs and testing for
shorts to case.
12.27.1
9-wire remote or remote core processor with remote transmitter installation
If you have a 9-wire remote installation or a remote core processor with remote transmitter (see
Section 1.3 and refer to Appendix B for diagrams):
1. Power down the transmitter.
2. If the transmitter is in a hazardous area, wait five minutes.
3. Remove the end-cap from the core processor housing.
4. Unplug the terminal blocks from the terminal board.
5. Using a digital multimeter (DMM), check the pickoff coils listed in Table 12-13 by placing the
DMM leads on the unplugged terminal blocks for each terminal pair. Record the values.
6. There should be no open circuits, i.e., no infinite resistance readings. The LPO and RPO
readings should be the same or very close (± 5 ohms). 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.
7. Leave the core processor terminal blocks disconnected. At the sensor, remove the lid of the
junction box and test each sensor terminal for a short to case by placing one 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.
Table 12-13
Coils and test terminal pairs
Coil
Test terminal pair
Colors
Drive coil
Brown to red
Left pickoff coil (LPO)
Green to white
Right pickoff coil (RPO)
Blue to gray
Resistance temperature detector (RTD)
Yellow to violet
Lead length compensator (LLC) (all sensors except CMF400 I.S. and T-Series)
Composite RTD (T-Series sensors only)
Fixed resistor (CMF400 I.S. sensors only)
Yellow to orange
Summary of Contents for MICRO MOTION 1500
Page 10: ...viii Micro Motion Series 1000 and Series 2000 Transmitters ...
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