Siemens SIMATIC Manual page 414

Analog modules
6.11 Analog input module SM 331, AI 6 x TC isolated (6ES7331-7PE10-0AB0)
Wiring: Thermocouple with external compensation
With this type of compensation, the temperature of the terminals at the reference junction is
established using a Pt 100 Klima resistance thermometer with a temperature range of -145
°C to +155 °C (see terminals 35, 36, 39, and 40).
①
Thermocouple with terminal for external temperature compensation via copper wire at front connector
②
Backplane bus interface
③
Analog digital converter (ADC)
④
External cold spot comparison (ADC and current source)
Figure 6-33 External compensation
If no Pt 100 resistance thermometer is available, the reference junction can be read using a
thermoresistor module. The measured temperature values are then transferred to module AI
6 x TC via data record 2 (for details on the structure of data record 2, see the figure
"Structure of data record 2 for TC").
414
S7-300 Module data
Manual, 06/2017, A5E00105505-AJ