Siemens SIMATIC ET 200S Manual page 405

Non-isolated measuring sensors
The non-isolated measuring sensors are connected to the local ground potential.
You must connect M
interference, potential differences U
locally distributed measuring points.
If the permitted value for U
the measuring points.
Figure 13-2 illustrates the connection of non-isolated measuring sensors to a
floating analog input module.
Non-isolated
measuring
sensors
Figure 13-2
Operating four-wire measuring transducers on an external voltage supply
If there is isolation between the output and the supply of the measuring transducer,
you can connect it to the 2AI I 4WIRE without additional connections.
If there is no isolation between the output and the supply of the measuring
transducer, you can connect it to the 2AI I 4WIRE only if the reference potential of
the power supply voltages (24 VDC) is the same.
If there is an increase in interference radiation, a connection between M– and M
on the terminal module of the 2AI I 4WIRE is recommended.
ET 200S Distributed I/O System
EWA-4NEB780602402-09
to the ground potential. Depending on local conditions or
ANA
is exceeded, there must be equalizing lines between
CM
U
CM
Potential
equalizing line
Connection of non-isolated measuring sensors to a floating analog input
module
(static or dynamic) can occur between the
CM
M+
M–
M+ ADC
M–
M
ANA
U
ISO
Ground bus
Analog Electronic Modules
L+
M
Backplane
bus
ana
13-21