Siemens SIMATIC Manual page 413

Terminal assignment
The figures below show various connection possibilities. These examples apply to all
channels (channels 0 to 5).
Wiring: Thermocouple with internal compensation
With this kind of compensation, the module detects the temperature at the reference junction
of the connector.
①
Thermocouple with compensating line (extension) to front connector
②
Backplane bus interface
③
Analog digital converter (ADC)
④
External cold spot comparison (ADC and current source)
Figure 6-32 Internal compensation
S7-300 Module data
Manual, 06/2017, A5E00105505-AJ
6.11 Analog input module SM 331, AI 6 x TC isolated (6ES7331-7PE10-0AB0)
Analog modules
413