Siemens S5-135U/155U Manual De Usuario

9-17

System Manual
C79000-G8576-C199-06

Observe the following information when connecting the sensors.

With isolated sensors, it is possible for the measuring circuit to develop a
potential with respect to ground which exceeds the permissible potential
difference U

<M>CM

 (see maximum values of the individual modules). To

prevent this, you must connect the negative potential of the sensor to the
reference potential of the module (0 V  bus).

Temperature measurement on a busbar with insulated thermocouples

In the worst case, the measuring circuit can develop an excessively high
potential on account of a static charge or contact resistances. This must be
prevented with an equipotential bonding conductor.

The permissible potential difference (U

CM

) between the inputs and the 0 V

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.

Equipotential   Bonding Conductor

0 V Bus

+

–

U

E

A

D

Analog Input Module

Sensor, Isolated

MUX

M+

M–

#

Range 
Card for
4 Inputs

Figure 9-6 Measuring Circuit with Equipotential Bonding Conductor for the 460 Analog Input Module

Analog Input/Output Modules