Siemens SIMATIC S7-300 Module data Reference Manual

Analog Modules
4-45
Programmable Logic Controllers S7-300 Module Data
A5E00105505-03
4.8 Connecting Sensors to Analog Inputs
Introduction
You can connect different sensors to the analog input modules depending on the
measuring method; voltage and current sensors, and resistors.
This section contains general information that is generally applicable to all the
connection options for sensors described in the sections that follow.
Cables for analog signals
To reduce electrical interference, you should use twisted-pair shielded cables for
the analog signals. The shield of the analog signal cables should be grounded at
both cable ends.
If there are potential differences between the cable ends, an equipotential bonding
current can flow over the shield, which leads to an interference of the analog
signals. In such a case, you should ground the shield at one end of the cable only.
Isolated analog input modules
In the case of isolated analog input modules, there is no electrical connection
between the reference point of the measuring circuit M
ANA
and the M terminal of
the CPU.
You must use isolated analog input modules if a potential difference U
ISO
can
occur between the reference point of the measuring circuit M
ANA
and the
M terminal of the CPU. An equipotential bonding conductor between the M
ANA
terminal and the M terminal of the CPU ensures that U
ISO
does not exceed the
permitted value.
Non-isolated analog input modules
In the case of the non-isolated analog input modules, you must establish a
connection between the reference point of the measuring circuit M
ANA
and the M
terminal of the CPU or IM 153. To do so, connect the M
ANA
terminal with the M
terminal of the CPU or IM 153. A potential difference between M
ANA
and the M
terminal of the CPU or IM 153 can result in corruption of the analog signal.
Limited potential difference UCM
Only a limited potential difference U
CM
(common mode voltage) may occur
between the measuring lines M– of the input channels and the reference point of
the measuring circuit M
ANA
. In order to prevent the permissible value from being
exceeded, you must take different actions, described below, depending on the
potential connection of the sensors.

Siemens SIMATIC S7-300 Module data Specifications

General

Series	S7-300
Manufacturer	Siemens
Protection Class	IP20
System	SIMATIC S7-300
Digital Inputs	Varies by module
Digital Outputs	Varies by module
Analog Inputs	Varies by module
Analog Outputs	Varies by module
Central Processing Unit	Varies by CPU model
Supply Voltage	24V DC or 120/230V AC
CPU Type	Varies (e.g., CPU 312, CPU 315, etc.)
Memory	Varies by CPU model
Communication Interfaces	MPI, PROFIBUS
Programming Languages	LAD, FBD, STL, SCL, GRAPH
Operating Temperature	0°C to 60°C
Storage Temperature	-40°C to 70°C
Relative Humidity	10% to 95% (non-condensing)