Collect Pickoff Voltage Data - Emerson Micro Motion 2700 Configuration And Use Manual

Troubleshooting
To know whether your pickoff voltage is unusually low, you must collect pickoff voltage
data during the problem condition and compare it to pickoff voltage data from a period of
normal operation.
Drive gain and pickoff voltage are inversely proportional. As drive gain increases, pickoff
voltages decrease and vice versa.
Table 10-6:
Possible cause
Cavitation or flashing; settling
of two-phase or three-phase
fluids
Faulty wiring runs between
the sensor and transmitter
Process flow rate beyond the
limits of the sensor
Two-phase flow
The vibrating element is not
vibrating
Moisture in the sensor elec-
tronics
The sensor is damaged, or
sensor magnets may have be-
come demagnetized
10.27.1

Collect pickoff voltage data

Pickoff voltage data can be used to diagnose a variety of process and equipment
conditions. Collect pickoff voltage data from a period of normal operation, and use this
data as a baseline for troubleshooting.
Procedure
1.
2.
202
Possible causes and recommended actions for low pickoff voltage
Recommended actions
•
•
•
Verify wiring between sensor and transmitter.
Verify that the process flow rate is not out of range of the sensor.
Check for two-phase flow. See
•
•
•
•
Eliminate the moisture in the sensor electronics.
Replace the sensor.
Navigate to the pickoff voltage data.
Observe and record data for both the left pickoff and the right pickoff, over an
appropriate period of time, under a variety of process conditions.
Micro Motion Model 2700 Transmitters with Intrinsically Safe Outputs
Increase the inlet or back pressure at the sensor. Increasing
back pressure is recommended. Applying back pressure down-
stream from the sensor can prevent flashing inside the sensor
tubes. That way, if the process fluid is going to flash, it will do
so downstream from the sensor after it has been measured.
If a pump is located upstream from the sensor, increase the
distance between the pump and sensor.
The sensor may need to be reoriented or repositioned. Consult
the installation manual for your sensor.
Section
Check for plugging or deposition.
Ensure that the vibrating element is free to vibrate (no me-
chanical binding).
Verify wiring.
Test coils at sensor. See Section
10.25.
10.28.1.