Connection Of Sensors - Siemens S5-135U/155U System Manual

9.3.8

Connection of Sensors

Observe the following information when connecting the sensors.
Connection of With isolated sensors, it is possible for the measuring circuit to develop a
Current or Voltage
potential with respect to ground which exceeds the permissible potential
Sensors
difference U
prevent this, you must connect the negative potential of the sensor to the
reference potential of the module (0 V bus).
Example:
Temperature measurement on a busbar with insulated thermocouples
Equipotential In the worst case, the measuring circuit can develop an excessively high
Bonding
potential on account of a static charge or contact resistances. This must be
prevented with an equipotential bonding conductor.
The permissible potential difference (U
bus must not be exceeded.
Depending on the system or type of sensor, the potential difference must be
kept in the permissible region with epuipotential bonding.
Sensor, Isolated
+
U
E
–
Figure 9-6 Measuring Circuit with Equipotential Bonding Conductor for the 460 Analog Input Module
System Manual
C79000-G8576-C199-06
(see maximum values of the individual modules). To
<M>CM
Analog Input Module
M+
MUX
Range
M–
Card for
4 Inputs
Equipotential Bonding Conductor
Analog Input/Output Modules
) between the inputs and the 0 V
CM
A
#
D
0 V Bus
9-17