Installation, connecting up, commissioning   
4.1 Power supply 
  LOGO! CMR2020 / LOGO! CMR2040  
26  Operating Instructions, 09/2014, C79000-G8976-C356-01 
 
Protection of the external power supply 
If power is supplied to the module or station over longer power cables or networks, the 
coupling in of strong electromagnetic pulses onto the power supply cables is possible. This 
can be caused, for example by lightning strikes or switching of higher loads. 
The connector of the external power supply is not protected from strong electromagnetic 
pulses. To protect it, an external overvoltage protection module is necessary. The 
requirements of EN 61000-4-5, surge immunity tests on power supply lines, are met only 
when a suitable protective element is used. A suitable device is, for example, the Dehn 
Blitzductor BVT AVD 24, article number 918 422 or a comparable protective element. 
Manufacturer: 
DEHN+SOEHNE GmbH+Co.KG Hans Dehn Str.1 Postfach 1640 D-92306 Neumarkt, 
Germany 
 
Power supply 
Screw terminals for the power supply 
 
L+ = live wire, positive pole of the DC voltage 12/24 VDC 
M = negative pole/ground of the DC voltage 12/24 VDC 
  Functional ground 
•  Serves to improve electromagnetic compatibility and to specify a common reference poten-
tial for all signals. 
•  Is achieved efficiently by a connection to the DIN rail. 
 
Note 
Power supply unit of the CMR is not electrically isolated 
No electrical isolation means that the input and output circuits are not galvanically is
olated.