GE CGA 351, User Manual

Page: 81 / 133

Service and Maintenance 5-3
December 2004
Checking the
Thermocouple
To check the thermocouple temperature sensor used in the CGA 351,
complete the following steps:
!WARNING!
There are very hot surfaces in the sensor enclosure.
Touching any of these surfaces without heat resistant
gloves will result in serious burns.
Note:
For information regarding component locations and/or wiring
connections in an optional enclosure, see Appendix C.
1.
Locate the thermocouple (
TC
) leads on pin
+
(yellow - no number)
and pin
-
(red - no number) on terminal block
TB2
.
2.
Using a digital multimeter, measure the voltage across the
TC
terminals. One of the conditions listed in Table 5-1 below should
occur.
3.
Complete the action recommended in Table 5-1 above.
Note:
If a voltage reading other than those listed above is obtained,
refer to Figure 5-1 and/or Table 5-2 on page 5-4 to determine
the operating temperature of the sensor furnace. A standard
CGA 351 operates at a temperature of 700 °C.
Based on the recommended action in Table 5-1 above, proceed to the
appropriate section for further instructions.
Table 5-1: TC Voltage Reading at 700°C
Voltage Reading Recommended Action
25–31 mV
The temperature is good - proceed to the
oxygen sensor check on page 5-5.
<25 mV
The temperature is low - proceed to the
sensor furnace check on page 5-5.
0 mV reading
The TC is defective - proceed to the TC
replacement instructions on page 5-17.
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