Panametrics CGA 351, User Manual, Page: 79 / 119

CGA 351 User’s Manual 73
Chapter 5.
5.1.2.3 Checking the Oxygen Sensor
If the thermocouple voltage was within the normal range, the troubleshooting sequence should continue here.
Note: For information regarding component locations and/or wiring connections in an optional enclosure, see
Appendix C.
1. Disconnect the oxygen sensor ( O2 ) leads (white
+
,
-
) from terminal block TB2 .
2. Using a digital multimeter, measure the resistance between the two disconnected oxygen sensor leads.
3. If the measurement indicates an open loop (OL), adjust the clips to make certain they are making good contact
with the oxygen sensor and take another reading. If an open loop is still measured, the oxygen sensor is defective
and must be replaced.
Note: A cold sensor will always indicate an open loop (OL).
If the oxygen sensor tests good, proceed to the next section to continue the troubleshooting procedure.
5.1.2.4 Checking the Sensor Furnace
If the sensor furnace operating temperature was too low, the troubleshooting sequence should resume here.
Note: For information regarding component locations and/or wiring connections in an optional enclosure, see
Appendix C.
1. Disconnect the sensor furnace ( HEATER ) leads (white 1 , 2 ) from terminal block TB2 .
2. Using a digital multimeter, measure the resistance across the disconnected sensor furnace leads. One of the
conditions listed in Table 135 below should occur.
Note: The sensor furnace impedance may also be checked in the User Program. Proceed to the Diag>Impedance
prompt, as described on page 66 (also, see Figure 3-1 on page 25), and display the current value.
3. If the sensor furnace is good, reconnect the sensor furnace leads to terminal block TB2 .
Based on the recommended action in Table 135 above, proceed to the appropriate section for further instructions.
5.1.2.5 Checking the Sensor Furnace Voltage
If the sensor furnace impedance test indicated that the sensor furnace is good, continue the troubleshooting
procedure here.
Note: For information regarding component locations and/or wiring connections in an optional enclosure, see
Appendix C.
1. Using a digital multimeter, measure the sensor furnace AC input voltage on terminal block TB2 . See Figure 6 on
page 14 for the location of TB2 and the HEATER pins. One of the conditions listed in Table 136 below should occur.
Table 135: Sensor Furnace Resistance Reading
Resistance Reading Recommended Action
approx. 66 ohms
The sensor furnace is good - check the
furnace voltage input (see page 73).
open loop (OL)
The sensor furnace is bad - replace the
sensor furnace (see page 81).
Table 136: Furnace Voltage Reading
Voltage Reading Recommended Action
approximately
full line voltage
Defective digital display unit - replace
the digital display (see page 84).
no voltage present
There is no power reaching the sensor
furnace - proceed with the next step.