3. SPECIFICATIONS
MELSEC-A
3-21
3.8.7
Pt100 cold junction compensation enable/disable designation
The AJ65BT-68TD can designate the enabling/disabling of the cold junction compensation by the
Pt100 temperature-measuring resistor.
By designating the enabling/disabling of the cold junction compensation by the Pt100 temperature-
measuring resistor, the detected temperature value to be stored in the remote register may be
switched between the value obtained using the Pt100 temperature-measuring resistor and not using
the Pt100 temperature-measuring resistor (when performing cold junction compensation externally).
The enabling/disabling of cold junction compensation by the Pt100 temperature-measuring resistor is
performed using the Pt100 cold junction compensation disable flag (RY (n+5) 7).
Setting Description
ON
Do not use the Pt100 temperature-measuring resistor for cold junction compensation.
OFF
Use the Pt100 temperature-measuring resistor for cold junction compensation.
(1) When using the Pt100 temperature-measuring resistor for cold junction compensation
The cold junction compensation is automatically performed by using the Pt100 temperature-
measuring resistor supplied with the AJ65BT-68TD.
Pt100
AJ65BT-68TD
Compensating conductor (copper)
Temperature measurement target
Thermocouple
(2) When performing cold junction compensation externally
Perform the following when the cold junction compensation accuracy (±1 °C) by the Pt100
temperature-measuring resistor supplied with the AJ65BT-68TD may not be ignored as a
tolerance. Since the module may be guided without any change in thermal electromotive force
generated at the tip of the thermocouple, the cold junction compensation accuracy may be
increased by installing a high accuracy temperature controller based upon 0
°
C* to outside of the
module.
* The temperature controller based upon 0
°
C has a structure in which a thermocouple and lead
wire are connected inside a pot, inside of which is maintained at 0°C.
Therefore, the thermal electromotive force generated at the contact point of the thermocouple
and contact area of the lead wire is 0 V, preventing the excess thermal electromotive force that
leads to errors in readings.
AJ65BT-68TD
Compensating conductor (copper)
Temperature measurement target
Thermocouple
Temperature controller
based upon 0°C
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Содержание AJ65BT-68TD
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