Hioki Super megohm SM7110 - Page 174

Appx.6
Countermeasures Against Noise
Conductive noise can be monitored with the Hioki 3145 Noise HiLogger while measures are taken. If the
penetration path has been specied, follow the measures shown in Figure 6.
L
N
PE
L
N
PE
The instrument
Isolation
Isolation
Motor
Power line
Line from a di󰀨erent
system
Welding
machine
Inverter
Controller
(Computer, PLC)
Common mode lter in
the penetration path
Separating the power line
Figure 6 Conductive Noise Countermeasures
Separating the power line
It is best to connect power systems and welding machines to a power from a di󰀨erent system than the
instrument.
Install the common mode lter (EMI choke) to the penetration path.
Common mode lters are more e󰀨ective if you choose ones with high-impedance and install several of them.
Insulation
Optically isolating the control line will improve the susceptibility to noise.
In Addition, optically isolating the power line with a noise-cut transformer will improve the susceptibility to noise
improves.
However, keep in mind that if the ground line is shared by the source side wiring of the transformer and the
load side wiring of it, the e󰀨ect may be diminished.