X20 system modules • Temperature modules • X20ATC402
2458
X20 system User's Manual 3.10
External temperature compensation
External compensation does not require the PT1000 values to be converted internally in the module. Instead, the
reference temperatures have to be pre-processed in the program before being stored in the module. A separate
register is available for each temperature channel to transfer an externally pre-processed compensation value.
In the following example, the compensation value is determined using the X20AT2311 temperature input module
and a PT100 sensor on the intermediate terminal. The cold junction temperature determined externally is then
made available to the X20ATC402 module via the respective I/O data points.
Since sensors A and B aren't needed for temperature compensation, the respective terminal points need to be
bypassed.
+
_
+
_
+
+
_
_
TC
1
TC
2
GND
+24 VDC
GND
+24 VDC
AT
AT
X20AT2311 X20ATC402
PT100
Intermediate terminal
Copper wire
4.31.8.7 Input circuit diagram
Channel 1
A/D
converter
Channel 6
Input value
I/O status
LED (green)
x
PT1000- x
+V
CC
TC+ x
TC- x
+LB
-LB
Sensor 2
Sensor 1
