Emerson Rosemount 8750W Reference Manual page 184

Troubleshooting
March 2016
Table 9-7. Common Magmeter Issues
Symptom Potential cause
Reading does •Transmitter, control system, or
not appear to be other receiving device not
within rated configured properly
accuracy
•Electrode Coating
•Gas/air in line
•Moisture problem
•Insufficient
upstream/downstream pipe
diameter
•Cables for multiple magmeters
run through same conduit
•Improper wiring
•Flow rate is below 1 ft/s
(specification issue)
•Auto zero was not performed
when the coil drive frequency
was changed from 5 Hz to 37 Hz
•Sensor failure–shorted
electrode
•Sensor failure–shorted or open
coil
•Transmitter failure
172
Corrective action
•Check all configuration variables for the transmitter, sensor,
communicator, and/or control system
•Check these other transmitter settings:
•Sensor calibration number
•Units
•Line size
•Perform a loop test to check the integrity of the circuit
•Enable Coated Electrode Detection diagnostic
•Use bullet-nose electrodes
•Downsize sensor to increase flow rate above 3 ft/s
•Periodically clean sensor
•Move the sensor to another location in the process line to
ensure that it is full under all conditions
•Perform the sensor tests - see
•Move sensor to a new location with five pipe diameters
upstream and two pipe diameters downstream if possible
•Use dedicated conduit run for each sensor and transmitter
•If electrode shield and electrode signal wires are switched, flow
indication will be about half of what is expected. Check wiring
diagrams.
•See accuracy specification for specific transmitter and sensor
•Set the coil drive frequency to 37 Hz, verify the sensor is full,
verify there is no flow, and perform the auto zero function
•Perform the sensor tests - see
•Perform the sensor tests - see
•Verify transmitter operation with a Rosemount 8714
Calibration Standard or replace the electronics board
Reference Manual
00809-0300-4750, Rev CA
Table 9-8 on page 175
Table 9-8 on page 175
Table 9-8 on page 175
Troubleshooting