Emerson Rosemount5081, Instruction Manual, Page: 100 / 152

3. Measure the resistance between the RTD IN and RETURN leads. For a thermistor,
measure the resistance between the two leads.
4. If the temperature is open or shorted, replace the sensor.
5. In the meantime, use manual temperature compensation.
SenSE OPEn
Most Rosemount sensors use a Pt100 or Pt1000 in a three-wire configuration. The in and
return leads connect the RTD to the measuring circuit in the analyzer. A third wire, called
the sense line, is connected to the return lead. The sense line allows the analyzer to correct
for the resistance of the in and return leads and to correct for changes in lead wire
resistance with changes in ambient temperature.
1.
Verify all wiring connections, including wiring in a junction box if one is being used.
2. Disconnect the RTD SENSE and RTD RETURN wires. Measure the resistance between
the leads.
It should be less than 5 Ω.
3. If the sense line is open, replace the sensor as soon as possible.
The transmitter can be operated with the sense line open. The measurement will be
less accurate because the transmitter can no longer compensate for lead wire
resistance. However, if the sensor is to be used at approximately constant ambient
temperatures, the lead wire resistance error can be eliminated by calibrating the
sensor to the measurement temperature. Errors caused by changes in ambient
temperature cannot be eliminated.
4. To make the error message disappear, connect the RTD SENSE and RETURN
terminals with a jumper.
OFFSEt Err
The OFFSEt Err message appears if the zero offset (in mV) exceeds the programmed limit.
Before increasing the limit to make the OFFSEt Err message disappear, check the following:
1.
Verify that the reference meter is working properly and is properly calibrated.
2. Verify that the process sensor is working. Check its response in a solution of known
conductivity.
3. If the transmitter is standardized against the conductivity determined in a grab
sample, be sure to measure the conductivity before the temperature of the grab
sample changes more than a few degrees.
4. Verify that the process sensor is fully immersed in the liquid.
If the sensor is not completely submerged, it may not properly measure the
conductivity of the process liquid.
5. Check the sensor for cleanliness. If the sensor looks fouled or dirty, clean it.
Refer to the sensor instruction manual for cleaning procedures.
Diagnostics and troubleshooting
90 Rosemount 5081