See Figure 11-4. The in and return leads are used to measure the resistance of the RTD. The
third lead, called the sense 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 lead resistance caused by changes in ambient temperature.
Procedure
1. Check wiring. See Figure 4-4 or Figure 4-5.
2. Disconnect the sense and return wires and measure the resistance between them.
It should be less than 1 Ω. See Figure 4-4 or Figure 4-5. Even though the sense line is
open, the sensor is still usable.
3. Use a wire jumper to connect the sense and return terminals on the sensor terminal
strip.
The temperature reading will no longer be corrected for the lead resistance, nor will
the transmitter be able to compensate for changes in ambient temperature. The
error could be several °C or more.
4. Replace the sensor.
11.4.4 Sensor Temperature High or Low
The sensor RTD is most likely miswired.
1. Check wiring connections.
2. Disconnect the RTD in and return leads and check the resistance between them.
See Figure 4-4 or Figure 4-5. The resistance should be close to the values given in
Section 11.7.2.
3. Replace the sensor.
11.5 Troubleshooting when no error message is
showing
Problem See Section
Zero current was accepted, but the current is outside
the range -10 to 15 nA.
Section 11.5.1
Error or warning message appears while zeroing the
sensor (zero current is too high).
Section 11.5.1
Zero current is unstable. Section 11.5.2
Sensor can be calibrated, but the current is too low. Section 11.5.3
Process readings are erratic or wander. Section 11.5.4
Readings drift. Section 11.5.5
Readings are too high. Section 11.5.6
Troubleshooting
90 Rosemount TCL
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