Analog modules
6.9 Analog input module SM 331; AI 8 x RTD; (6ES7331-7PF01-0AB0)
S7-300 Module data
382 Manual, 06/2017, A5E00105505-AJ
Figure 6-22 Unused channel
Always use channel n (in this case channel 0) for measurement
Short-circuit unused channels (in this case channel 1)
connect them in order to avoid
diagnostic results with a resistance of the rated range (eg.100 ohms at Pt 100)
Incorrect wiring of the 3-wire connection can result in unpredictable operation of the module
and dangerous conditions in the plant.
Wiring: 3-wire connection
With a 3-wire connection to the SM 331; AI 8 x RTD, you need to set a jumper between M
+
and I
C+
.
Always ensure that the connected I
C
and M cables are directly to the resistance
thermometer.
Wiring: 2-wire connection
With a 2-wire connection to the SM 331; AI 8 x RTD, you need to set a jumper between M
+
and I
C+
as well as M
-
and I
C-
.
There is no compensation of the line resistance with a 2-wire connection. The line
resistances are also measured!