Siemens Simatic S7-400 - Manual (Page 536)

Interface Submodules
13-40
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Connection of Current Sensors as Two-Wire and Four-Wire Transducers
Figures 13-16 and 13-17 show you how to connect current sensors as two-wire
and four-wire transducers to analog input modules.
The 24 V voltage is supplied to the two-wire transducer via a protected output (L1
+
,
L2
+
). The two-wire transducer converts the measured variable to a current of 4 to
20 mA. The range 4 to 20 mA is converted to the required format by a software
driver function.
Four-wire transducers have a separate supply voltage.
Two-wire
transducers
Two-wire
transducers
+24 V
Sensor,
e. g. pressure
gauge
P
P
+
-
+
-
L
+
M
L1
+
M
0-
MI
1+
M
1-
0 V
MI
0-
V
m
V
m
4 to 20
mA
4 to 20
mA
Figure 13-16 Connection of Two-Wire Transducers
+24 V
transducer Four-wire
+
-
+
-
Sensor,
e. g. pressure
gauge
P
P
L
+
M
MV
0+
M
0-
MV
1+
M
1-
V
CM1
V
CM0
0 V
Figure 13-17 Connection of Four-Wire Transducers