Emerson Rosemount5081, Инструкция по эксплуатации, Страница: 69 / 152

rEF FAIL
rEF FAIL is an electrode fault message. rEF FAIL means that the reference impedance
exceeds the programmed reference high fault (RFH) limit. A plugged or dry reference
junction is the usual cause of a high reference impedance. High reference impedance also
occurs if the sensor is not submerged in the process liquid or if inappropriate limits have
been entered into the transmitter.
If the measurement system was previously commissioned and operating correctly, rEF FAIL
likely means a real problem exists. However, if the system is being started up or if the
advanced diagnostic feature is being used for the first time,
rEF FAIL could be caused by a
miswired sensor or by programmed limits that are not correct for the sensor.
NOTICE
rEF FAIL is a sensor diagnostic message. All sensor diagnostic messages are optional. They can
be turned off.
Troubleshooting flowchart - rEF FAIL
1. Be sure the sensor is completely immersed in the process liquid.
• If the diagnostic message disappears, the sensor is in good condition.
• If the diagnostic message remains, go to Step 2.
2. Check that the sensor is properly wired to the transmitter. Be sure the reference in
wire is attached to TB-7 and the solution ground wire is attached to TB-8.
NOTICE
TB-8 means terminal 8 on the terminal board.
• If correcting wiring problems makes the diagnostic message disappear, the
sensor is in good condition.
• If the wiring is correct and the message still remains, go to Step 3.
3. Measure and make a note of the reference impedance ( rIMP ). See Section 8.1.7 .
• If the reference impedance is low (< 70 kilohms)...
a. The reference electrode is in good condition. pH sensors manufactured by
Rosemount use low impedance silver/silver chloride reference electrodes.
b. The reference failure high (RFH) limit is probably set too low. Change the limit
to a value about 50 kilohms greater than the measured reference impedance.
If
rEF WARN was also displayed, change the reference warning high (RWH)
limit to about 25 kilohms above the measured reference impedance.
• If the reference impedance is high (> 70 kilohms)...
a. The sensor may be dirty, in which case cleaning it will lower the impedance. If
the sensor is rebuildable, the reference electrolyte may be depleted. Finally,
the sensor may be in good condition. The warning and failure limits are
simply set too high.
Diagnostics and troubleshooting
Instruction Manual 59