Siemens SIMATIC ET 200AL System Manual page 1449

Thermocouples
5.3 Compensation for the reference junction temperature
Temperature condition with "Fixed reference temperature" setting
The figure below shows the connection options for thermocouples provided the temperature
of the module is kept at a fixed reference temperature (20 °C), for example by installing it in
an air-conditioned switch cabinet. The reference junction is in the module.
①
②
③
Figure 5-10
92
Thermocouple without compensating line
Thermocouple via compensating line
Compensating line (same material as thermocouple)
Example 1: Connecting a thermocouple to an analog module for compensation with
"fixed reference temperature"
Analog value processing
Function Manual, 06/2014, A5E03461439-AC