5-7
5.2.2 Grounding
In situations of excess noise
Under normal conditions, the inherent noise resistance is sufficient. However, in situations of excess
noise, ground the instrument to increase noise suppression.
Exclusive grounding
- 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.
Note:
Depending on the surroundings in which the equipment is used, grounding may cause problems.
Since the power supply line of the FP0/FP0R expansion unit is connected to the function earth through a
varistor, if there is an irregular potential between the power supply line and earth, the varistor may be
shorted.
As for the FP0R control unit, since its power supply line is connected to the function earth through a
high-voltage capacitor, it is no problem.
Do not ground the function earth terminal when grounding a plus (+) terminal of the power.
Do not ground the FP0R function earth terminal when grounding a plus (+) terminal of the power.
In some computers, the SG terminal of RS232C port and connector shielding are connected.
In addition, an FP0R tool port shielding and function earth terminal are connected.
Therefore, the GND terminal of FP0R and the function earth terminal are connected if the computer is
connected.
Especially when the FP0R is connected to a computer with a plus (+) terminal grounded, the GND
terminal is in the state that the voltage of -24 V is applied. As a result, short circuit occurs which may
lead to the breakage of FP0R and its neighboring parts if the GND terminal is connected to the earth
terminal in that state.
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