Siemens SIMATIC FM 351 Manual page 27

Auxiliary Power Supply for the Encoders (1L+, 1M)
Here, you connect the 24 V DC auxiliary power for the encoders. The reference
potential of this power supply (1M) is not connected with the chassis of the load
current supply (2M) in the FM 351.
The 24 V DC auxiliary power for the encoders is monitored for undervoltage and
chassis wire break.
The 24 V DC auxiliary voltage for the encoders is converted internally to 5.2V DC.
This means that 24 V DC and 5.2 V DC are available on the encoder interface (sub
D female connector X2 and X3) for the different types of encoders.
! Caution
Make sure that the polarity of the 24 V DC auxiliary power supply for the encoders
(1L+, 1M) is correct.
If you connect the 24 V DC auxiliary power supply for the encoders and
accidentally reverse the polarity, this will damage the module to such an extent that
it must be replaced.
Auxiliary Power Supply for the Load Current (2L+, 2M)
You connect a 24 V auxiliary supply for the load current of the digital outputs at
terminals 2L+ and 2M.
Caution
!
Make sure that the polarity of the 24 V auxiliary power for the load current (2L+,
2M) is correct.
If you connect the 24 V DC auxiliary power for the load current and accidentally
reverse the polarity, this will damage the module to such an extent that it must be
replaced.
Note on Wiring 24 V DC
When wiring up the module, remember that the terminals 1L+,1M and 2L+, 2M
must be connected for the module to operate correctly.
If you connect 1L+, 1M and 2L+, 2M to separate power supplies, the
synchronization of the axes is retained if there is an outage of the auxiliary power
supply for the load current.
FM 351 Positioning Module
C79000-G7076-C351-02
Wiring the FM 351
4-5