Siemens SIMATIC S7-300 Module data - Connection of Thermocouples with Compensation Box to an Isolated AI

Analog Modules
4-62
Programmable Logic Controllers S7-300 Module Data
A5E00105505-03
Connecting thermocouples with compensating box
If all thermocouples connected to the inputs of the module have the same
comparison point, you compensate as follows:
M+
M–
M+
M–
Backplane
bus
ADC
M
L+
Compensating
leads (same
material as
thermocouple)
Box
Comp.
Ref. junction
ML+
Copper
wire
COMP
–
/M
ANA
COMP
+
Thermo-
couples
Logic
Figure 4-24 Connection of Thermocouples with Compensation Box to an Isolated AI
Note
Use compensating boxes with a reference junction temperature of 0C for
analog input modules.
Recommended compensating box
We recommend you to use a comparison point (with integrated power supply unit)
from Siemens as a compensating box. You will find the necessary ordering data in
the table below.