Siemens Simatic S7-400 - Manual (Page 274)

Analog Modules
5-58
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Connecting Thermocouples and Resistance Thermometers
Connect the resistance thermometer to channel 0 of the module. Make sure that
you parameterize the “RTD on Channel 0“ reference junction in STEP 7 for each
channel that has a thermocouple connected to it.
If all thermocouples connected to the inputs of the module have the same
comparison point, you compensate as follows:
M
+
M
–
M
+
M
–
Reference
junction
Incoming line (Cu)
Equalizing line (same
material as
thermocouple)
M
–
I
I
C+
C–
M
+
RTD on Channel 0
Figure 5-20 Connection of Thermocouples of the Same Type with External Compensation
by Means of a Resistance Thermometer, Connected to Channel 0