Cold Junction Compensation Resistor Disconnection Detection Function - Mitsubishi Electric MELSEC iQ-R Series User Manual

1.9
Cold Junction Compensation Resistor
Disconnection Detection Function
This function outputs an error when disconnection of a cold junction compensation resistor (RTD) is detected. Only the
thermocouple input module can use the function.
Notification of disconnection
• 'Error flag' (XF) turns on.
• The ERR LED turns on.
• An error code is stored in 'Latest error code' (Un\G0). ( Page 83 List of Error Codes)
• The temperature conversion stops for all the channels where conversion is enabled. At that time, 'Conversion completed
flag' turns off for all the channels.
• 'CH1 Measured temperature value' (Un\G400) holds a value just before the disconnection.
Relationship of disconnection detection and conversion enable/disable setting
Disconnection detection is executed when With cold junction compensation (0) is set in 'Cold junction compensation with/
without setting' (Un\G298) and the conversion is enabled for one channel or more. The following table shows the relationship
of disconnection detection and setting state of each item.
Connection status
RTD
No disconnection
RTD
Disconnection
No connection
Disconnection is not detected when the conversion is disabled for all channels.
Recovery from disconnection
Even if the connection of a cold junction compensation resistor (RTD) is re-established, the temperature conversion is not
restarted. Turn on and off 'Error clear request' (YF) to restart the temperature conversion.
Cold junction compensation
with/without setting
With cold junction compensation
RTD+
RTD-
RTDG
Without cold junction compensation
With cold junction compensation
RTD+
RTD-
Without cold junction compensation
RTDG
With cold junction compensation
RTD+
RTD-
RTDG
Without cold junction compensation

1.9 Cold Junction Compensation Resistor Disconnection Detection Function

State of conversion enable/
disable setting
Conversion enabled for one or
more channel
Conversion disabled for all
channels
Conversion enabled for one or
more channel
Conversion disabled for all
channels
Conversion enabled for one or
more channel
Conversion disabled for all
channels
Conversion enabled for one or
more channel
Conversion disabled for all
channels
Conversion enabled for one or
more channel
Conversion disabled for all
channels
Conversion enabled for one or
more channel
Conversion disabled for all
channels
1 FUNCTIONS
1
'Error flag' (XF)
OFF
ON
OFF
ON
OFF
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