A Measured Temperature Value Cannot Be Read; A Measured Temperature Value Does Not Change - Mitsubishi Electric MELSEC iQ-R Series User Manual

A measured temperature value cannot be read

Check item
Check whether an analog signal line is disconnected from the temperature
input module.
Check whether a thermocouple and compensation lead wire are correctly
connected to the thermocouple input module.
Check whether a resistance temperature detector is correctly connected to the
RTD input module.
Check whether the CPU module is in the STOP state.
Check whether the offset/gain setting is correct.
Check whether the input range setting is correct.
Check whether Conversion disable (1) is set in 'CH1 Conversion enable/
disable setting' (Un\G500) of the channel to be used.
Check whether 'Operating condition setting request' (Y9) has been executed.
*1 The temperature conversion does not start when 'Operating condition setting request' (Y9) is on. After turning on this signal (Y9), check
that 'Operating condition setting completed flag' (X9) is off, and then turn off the signal (Y9).

A measured temperature value does not change

Check item
Check whether disconnection of a thermocouple or compensation lead wire is detected in the
thermocouple input module.
Check whether disconnection of a cold junction compensation resistor (RTD) is detected in the
thermocouple input module.
Check whether disconnection is detected in the RTD input module.
Action
Visually check signal lines and correctly connect analog signal lines.
Correctly connect a thermocouple or compensation lead wire to the
thermocouple input module. The following are the check points.
• A shielded cable for the used channel is grounded or not.
• The thermocouple and compensation lead wire are reversely connected or
not.
Correctly connect a resistance temperature detector to the RTD input module.
The following is the check point.
• A shielded cable for the used channel is grounded or not.
Change the state of the CPU module to RUN.
Check that the offset/gain setting is correct. If the user range setting is used,
change it to the other input range and check that the temperature conversion
is performed correctly.
When the temperature conversion is correct, perform the offset/gain setting
again.
Check that the set input range is corresponding to the connected
thermocouple or connected resistance temperature detector using the
following buffer memory areas.
• Thermocouple input module: 'CH1 Range setting monitor (Thermocouple
type)' (Un\G430)
• RTD input module: 'CH1 Range setting monitor (Resistance temperature
detector type)' (Un\G430)
If the input range setting is not correct, set "Thermocouple type setting" or
"RTD type setting" of Module Parameter again.
Check 'CH1 Conversion enable/disable setting' (Un\G500) and correct the
value to Conversion enable (0) with the module parameter or a program.
Check that the measured temperature value is stored in 'CH1 Measured
temperature value' (Un\G400) by turning on and off 'Operating condition
setting request' (Y9). If the stored value is correct, check the program to verify
the description of 'Operating condition setting request' (Y9).
Action
Eliminate the cause of disconnection, by replacing
the thermocouple or compensation lead wire for
instance, and check 'CH1 Measured temperature
value' (Un\G400).
Eliminate the cause of disconnection, by replacing
the cold junction compensation resistor (RTD) for
instance, and check 'CH1 Measured temperature
value' (Un\G400).
Eliminate the cause of disconnection, by replacing
the resistance temperature detector for instance,
and check 'CH1 Measured temperature value'
(Un\G400).
3.3 Troubleshooting by Symptom
3 TROUBLESHOOTING
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