Emerson Rosemount FCL, Справочное руководство

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9.4.3 Sensor Out of Range
This warning message applies to the pH sensor only. It appears when the raw signal from
the pH sensor is greatly outside the range expected for a properly operating sensor.
Procedure
1. Confirm that the pH sensor is plugged into the VP cable labeled pH sensor.
2. Check wiring in the transmitter.
3. Replace the pH sensor.
9.4.4 Sensor Negative Reading
This warning message applies to the chlorine sensor only. The transmitter converts the
raw sensor current to ppm chlorine by subtracting the zero current from the raw current
and multiplying the result by a conversion factor. If the zero current is larger than the raw
current, the result will be negative.
Procedure
1. Check the zero current.
It should be less than about 10 nA.
2. If it is greater than 10 nA, repeat the zero step.
If the zero current is in the correct range, the negative reading might be the result
of the raw current or the senstivity being too low. A properly operating sensor
should generate between 250 and 350 nA for every 1 ppm free chlorine at pH 8.
3. Recalibrate the sensor. If necessary, clean or replace the membrane and check the
fill solution.
4. Replace the sensor.
9.4.5 Sensor RTD Sense Open
The transmitter measures temperature using a three-wire resistance temperature device
(RTD). See
Figure 9-5 . The transmitter uses the in and return leads to measure the
resistance of the RTD. The third lead, called the snese line, is connected to the return lead
at the sensor. The sense line allows the transmitter to correct for the resistance of the in
and return leads and to compensate for changes in wire resistance caused by changes in
ambient temperature.
Recommended actions
1. Check wiring.
2. Disconnect the sense and return wires and check the resistance between them.
3. Use a wire jumper to connect the sense and return terminals to the sensor terminal
strip.
The transmitter will no longer correct the temperature for lead resistance or
compensate for changes in ambient temperature. The error could be several °C or
more.
4. Replace the sensor.
Troubleshoot Reference Manual
May 2019 00809-0100-3412
92 Emerson.com/Rosemount