Emerson Series 3000 MVD User Manual

235

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.

If you have a remote core processor with remote transmitter installation:

1. Power down the transmitter.

2. If the transmitter is in a hazardous area, wait five minutes.

3. At the core processor:

a.

Remove the end-cap.

b.

Unplug the terminal blocks from the terminal board.

c.

Using a digital multimeter (DMM), check the pickoff coils listed in Table 22-16 by 
placing the DMM leads on the unplugged terminal blocks for each terminal pair. Record 
the values.

4. 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

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.

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

40 k

Ω – 50 kΩ

20 k

Ω – 25 kΩ

20 k

Ω – 25 kΩ