Siemens S5-135U/155U appendix Connection of Sensors, Current or Voltage

Analog Input/Output Modules

9.3.8Connection 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<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).
	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 (UCM) 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.

Sensor, Isolated

+

U E

±

Analog Input Module

M+

A

MUX

M± Range Card for

4 Inputs

#

D

0 V Bus

Equipotential Bonding Conductor

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

System Manual	9-17
C79000-G8576-C199-06