Siemens SIMATIC Manual page 415

Wiring: Thermocouple via reference junction
With this kind of compensation, the temperature of the terminals at the reference junction is
regulated at 0 °C or 50 °C.
①
Thermocouple via reference-junction terminal with copper wire at front connector
②
Backplane bus interface
③
Analog digital converter (ADC)
④
External cold spot comparison (ADC and current source)
⑤
Reference junction regulated at 0 °C or 50 °C, for example, via compensation box (for each channel) or a thermo-
stat
Figure 6-34 Reference junction
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
415