
Analog modules
5.13 Connecting thermocouples
S7-400 Automation System Module Data
236 Reference Manual, Edition 09/2009, A5E00850736-06
Connecting thermocouples using resistance thermometers
Connect the resistance thermometer to channel 0 of the module. Make sure that you
configure 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 module's inputs share a common reference junction,
compensate the circuit as follows:
1
2
34
M+
M-
M+
M-
M-
I
I
C+
C-
M+
M
+
: Measuring line (positive)
M
-
: Measuring line (negative)
I
C+
: Constant current line (negative)
I
C+
: Constant current line (negative)
(1) Compensating leads (same material as thermocouple)
(2) RTD on Channel 0
(3) Incoming line (Cu)
(4) Reference junction
Figure 5-18 Connection of thermocouples of the same type with external compensation by means of
a resistance thermometer, connected to channel 0
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