Yokogawa Single Channel Oxygen Analyzer System ZR22/ZR402 - Manual (Page 195)

IM 11M12A01-03E 12-11
12. Troubleshooting
The case where the Model ZR22 Detector is used:
(1) Stop the power to the converter.
(2) Remove the wiring from terminals 5 and 6 of the detector and measure the resistance
between these terminals. If the resistance value is out of the range of 1 to 1.6 k
⍀,
the cold junction temperature sensor is considered to be faulty. Replace that tem-
perature sensor with a new one.
(3) If the resistance value is within the above range, the cold junction temperature sensor
seems to be normal. Check whether or not the cable is broken or shorted out, and
whether the cable is securely connected to the terminals. Also, check that the
resistance of the wiring between the converter and detector is 10
⍀ or less.
(4) If there is no failure in the wiring, the electrical circuits inside the converter may
possibly fail. Contact the service personnel at Yokogawa Electric Corporation.
The case where the Model ZO21D Detector is used:
(1) Without stopping the power to the converter, remove the wiring from terminals 5 and
6 of the detector and measure the voltage between these terminals. If the voltage
between the terminals is out of the range of 0.4 to 0.7 V, the cold junction tempera-
ture sensor seems to be faulty. Replace the cold junction temperature sensor.
(2) If the voltage between the terminals is within the above range, the cold junction
temperature sensor seems to be normal. Check whether or not the cable is broken or
shorted out, and whether the cable is securely connected to the terminals. Also,
check that the resistance of the wiring between the converter and detector is 10
⍀ or
less.
(3) If there is no failure in the wiring, the electrical circuits inside the converter may
possibly fail. Contact the service personnel at Yokogawa Electric Corporation.
CAUTION
• The operating temperature range of the Model ZO21D Detector is -10
Њ C to 80Њ C
(except for the high-temperature detector ZO21D-H). Since a cold junction tempera-
ture alarm for this analyzer is not generated until the temperature exceeds 155
Њ C, if
the Model ZO21D Detector is used, be careful in controlling the ambient temperature
of the terminal block.
12.2.2.7 Alarm 11: Thermocouple Voltage Alarm
This alarm is generated when the emf (voltage) of the thermocouple falls below -5 mV
(about -170
Њ C) or exceeds 42.1 mV (about 1020Њ C). Whenever Alarm 11 is generated,
Error-2 (heater temperature failure) occurs.
(1) Breakage of the heater thermocouple signal wire between the converter and the
detector occurred, or the cable is not securely connected to the connecting terminals.
(2) The positive and negative poles of the heater thermocouple signal wiring are shorted
out in the wiring extension or at the connection terminals.
(3) A failure of the thermocouple at the detector heater assembly occurred.
(4) A failure of the electrical circuits inside the converter occurred.
<Locating cause of failure, and countermeasures>
(1) Stop the power to the converter.
(2) Remove the wiring from terminals 3 and 4 of the detector and measure the resistance
between these terminals. If the resistance value is 5
⍀ or less, the thermocouple
seems to be normal. If it is higher than 5
⍀, it may indicate the possibility that the
thermocouple has broken or is about to break. In this case, replace the heater unit
(refer to Section 11.1.3, “Replacement of the Heater Unit”).