Siemens SIMATIC ET 200SP F-AI 4xI 0(4) 20mA 2-/4-wire HF Series - Page 19

Connecting
3.1 Wiring and block diagram
Analog input module F-AI 4xI 0(4)..20mA 2-/4-wire HF (6ES7136-6AA00-0CA1)
Manual, 08/2018, A5E41448857-AB
19
External/internal sensor supply
The figures in section "Applications of the F-I/O module (Page 40)" show how you can
supply power to the sensors via an external sensor supply (for example, from another
module).
WARNING
If there is a short-circuit from L+ to Mn+, the input resistors could be destroyed, depending
on the selected interconnection type.
You can avoid this problem through proper wiring and use of the internal sensor supply.
When an external sensor supply is used, other suitable measures are necessary to protect
the input resistors (e.g. external fast 50 mA fuse in the input circuit of the F-module).
WARNING
External sensor supply
If you use an external sensor supply, you need to take into consideration the voltage dips
and voltage fluctuations when determining the safety function.
To ensure that the sensor functions problem-free, we recommend one of the following
options:
• Use a transducer with an appropriate battery backup or diagnostics.
or
• Use a
redundant
external sensor supply
or
•
Monitor
the external sensor supply for undervoltage/overvoltage, including shutdown of
the sensor supply in the event of a fault (single channel for SIL2; two-channel for SIL3).