Installation and Wiring 
 
FPΣ User's Manual 
80 
6.3.1 Grounding 
If necessary, ground the instrument to increase the noise resistance. 
 
NOTE
 
•  For grounding purposes, use wiring with a minimum of 2mm
2
. The 
grounding connection should have a resistance of less than 100Ω. 
•  The point of grounding should be as close to the PLC as possible. The 
ground wire should be as short as possible. 
•  If two devices share a single ground point, it may produce an adverse 
effect. Always use an exclusive ground for each device. 
OK
1
 
PLC 
2
 
Other device (inverter etc.) 
Risk of short circuits 
Depending on the surroundings in which the equipment is used, grounding may cause 
problems.  
Example1: 
Since the power supply lines of the FPΣ and of the FP0 expansion unit (24V DC and 0V 
terminal) are connected to the function earth (PE) through a varistor, the varistor may be 
shorted if there is an irregular potential between the power supply line and function earth. 
24V DC
PE
0V
 
Power supply line of FP
Σ
 or FP0 expansion unit 
Unit type  Varistor 
FPΣ C32, C28 
82V 
FPΣ C24 
56V 
FP0 expansion unit  39V