Emerson Rosemount5081 - Too Big; Bad Rtd, TEMP HI, TEMP LO, and Rtd Open; Ph in

See the sensor instruction sheet for details.
4. Replace the sensor.
0 too bIG
Normally, the transmitter will not accept a zero current until the current has fallen below a
reasonable value. See the calibration section for the analyte being determined for zero
currents. However, you can force the transmitter to accept the present current as the zero
value. The 0 too bIG warning appears if the current at the time the sensor is zeroed is
greater than 100 nA. Because the transmitter subtracts the zero current from the
measured current before converting the result to a concentraiton, zeroing too soon will
cause readings to be too low.
1. Allow adequate time, possibly as long as overnight, for the sensor to stabilize before
starting the zero routine.
2. Verifty that the solution used for zeroing the sensor contains no analyte.
Refer to the appropriate Calibration section for details.
3. Replace the sensor membrane and electrolyte solution and clean the cathode if
necessary.
See the sensor instruction sheet for details.
4. Replace the sensor.
bAd rtd, TEMP HI, TEMP LO, and rtd OPEn
These messages usually mean that the RTD (or themistor in the case of the Hx438 and
GX448 sensors) is open or shorted or there is an open or short in the connecting wiring.
1. See Section 8.4.12
2. Verify all wiring connections, including wiring in a junction box if one is being used.
3. Disconnect the RTD IN, RTD SENSE, and RTD RETURN leads or the thermistor leads
at the transmitter. Be sure to note the color of the wire and where it was attached.
Measure the distance between the RTD IN and RETURN leads. For a thermistor,
measure the resistance between the two leads. The resistance should be close to the
value in the table in Section 8.4.12. If the temperature element is open or shorted,
replace the sensor. In the meantime, use manual temperature compensation.
For oxygen measurements using the HX438, the Gx448, or other steam-sterilizable
sensor using a 22kNTC, the TEMP HI error will appear if the controller was not
properly configured.
pH In
pH In means the voltage from the pH measuring cell is too large.
1. Verify all wiring connections, including connections in a junction box.
2. Check that the pH sensor is completely submerged in the process liquid.
3. Check the pH sensor for cleanliness. If the sensor looks fouled or dirty, clean it.
Refer to the sensor instruction manual for cleaning procedures.
Diagnostics and troubleshooting
96 Rosemount 5081