Emerson 3081FG instruction manual Fault 1, Open Thermocouple

Instruction Manual

IB-106-3081 Rev. 1.5 September 2002

Model 3081FG

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26020024

Figure 6-5. Fault 1, Open Thermocouple

a.Fault 1, Open Thermocouple

The thermocouple connection is open. The fault displays as shown in Figure 6-5.

1.Refer to Figure 6-4and check the thermocouple wiring connections at terminals 8 and 10. Ensure the wires are properly connected.

2.Remove power. Disconnect the ther- mocouple wires (gray and red) from terminals 10 and 8. Measure the conti- nuity across the gray and red thermo- couple leads. The measurement should read approximately 1-2 ohms. Larger values indicate the thermocou- ple is open.

3.If the thermocouple is open, replace the oxygen probe per paragraph 5-2.

26020025

Figure 6-6. Fault 2, Reversed Thermocouple

b.Fault 2, Reversed Thermocouple Active

The thermocouple connections are re- versed. The fault displays as shown in Fig- ure 6-6.

1.Allow adequate time for the oxygen probe to reach operating temperatures. Probe temperatures below approxi- mately 500°C (932°F) may result in this fault.

2.Refer to Figure 6-4.Check the gray (to terminal 10) and red (to terminal 8) wires for the proper placement.

3.Using a multimeter, measure between terminals 8(-) and 10(+). If the reading is negative, the thermocouple wiring is reversed. Rewire as necessary.

4.If the wiring is correct and the probe is at operating temperature, then the transmitter electronics are bad. Re- place the PC board stack assembly per paragraph 5-1.

6-4 Troubleshooting Rosemount Analytical Inc. A Division of Emerson Process Management