Emerson MMI-20019043 Manuel D’Utilisation

12.28.1

Check the sensor coils

Checking the sensor coils can identify electrical shorts.

This procedure applies only to 9-wire remote-mount transmitters and remote transmitters with
remote core processors..

1.

Disconnect power to the transmitter.

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 

the coils. Record the values.

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

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

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