Yokogawa Single Channel Oxygen Analyzer System ZR22/ZR402 - Manual (Page 194)

IM 11M13A01-02E 12-9
12. Troubleshooting
12.2.2.5 Alarm 10: Cold Junction Temperature Alarm
This alarm is generated when the temperature of the cold junction located at the
terminal block of the detector falls below -25
؇C or exceeds 155؇C. Check the following:
Display “C.J.Temperature” in the detailed data display. If “C.J.Temperature” is
indicated as 200
؇C or -50؇C, the following can be considered.
(1) Breakage of the cold junction signal wires between the converter and the detector, or
the cable is not securely connected to the connecting terminals.
(2) The positive and negative poles of the cold junction signal wiring are shorted out in
the wiring extension or at the connection terminals.
(3) A failure of the cold junction temperature sensor located at the detector terminal
block occurred.
(4) A failure of the electrical circuits inside the converter occurred.
If “C.J.Temperature” exceeds 150
؇C or falls below -20؇C, the following can be
considered.
(1) The temperature of the detector terminal block is out of the operating temperature
range (-20
؇C to 150؇C).
(2) A failure of the cold junction temperature sensor located at the detector terminal
block occurred.
(3) A failure of the electrical circuits inside the converter occurred.
<Locating cause of failure and countermeasures>
Before proceeding to the following troubleshooting procedure, examine whether or not
the temperature of the detector terminal block is out of the operating temperature range.
The operating temperature range varies with the type of detector. If the detector
terminal block is out of its operating temperature range, take the measure to lower the
temperature, such as situating it so that it is not subjected to radiant heat.
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.