Siemens S5-135U/155U - Manual (Page 471)

9-89
System Manual
C79000-G8576-C199-06
The following figure shows the connection of sensors to the module. For
measurement with respect to ground, all the M- connection points are
interconnected internally on the module.
U E2
U E1
Analog Input Module
M+
M–
+
–
+
–
M+
U ISO
MUX
0 V Bus
U
E1/2: Input Voltage
U
ISO: Potential Difference
: Equipotential; this potential is established by the sensor reference potential
(external reference potential)
Figure 9-30 Connecting Sensors to the 466 Analog Input Module (Measurement with Respect to Ground)
The differential measurement is a method of compensating for interference
on the line. Each signal source is assigned its own signal reference line. The
differential measurement between signal line and signal reference line thus
compensates for the interference acting on both lines.
You must also short-circuit the unused channels with this measuring method
(jumper between M+ and M-).
Differential measurement is required:
S
if the sensors are at different potentials;
S
if various signal sources are not close to each other;
S
if there is a need to measure signals with high precision;
S
and when a high level of interference is expected.
Differential
Measurement
Analog Input/Output Modules