Siemens SIMATIC Manual page 255

Wiring and connecting thermocouples via compensating box
If all thermocouples connected to the module's inputs share a common reference junction,
compensate the circuit as follows:
Figure 4-15
Note
To compensate the analog input modules, always use compensation boxes with a reference
junction temperature of 0 °C.
Recommended compensating box
Use a compensating box with a reference junction. You must order compensating box from
external companies. Contact your Siemens representative or Industry Online Support on the
Internet (https://support.industry.siemens.com/cs/ww/en/).
S7-300 Module data
Manual, 06/2017, A5E00105505-AJ
Wiring and connecting thermocouples to electrically isolated analog inputs via
compensation box
Principles of analog value processing
4.6 Wiring and connecting thermocouples
255