Hioki ST5520-01 - Page 188

Appx.8
Inuence of Noise
Inuence of conductive noise
In addition to inductive noise superimposed on the equipment to be measured or measurement
leads, there is conductive noise. Conductive noise indicates noise superimposed on a power
line or control line, such as a USB, etc.
Various devices, including a motor, welder, inverter, etc. are connected to the power line.
When these devices are in operation or every time they start and stop, current spikes are
generated in the power supply. Due to the current spikes and power line wiring impedance,
signicant voltage spikes are generated in the power line and power ground line, which can
affect measurement equipment.
Noise may be generated from the controller control line in the same manner. The noise from
the controller power or the DC-DC converter inside the controller enters the measurement
equipment through the USB or EXT.I/O wiring. (Figure. Conductive noise entry route)
Instrument
RS-232C
EXT.I/O
USB
GP-IB
Controller
(PC, PLC)
Motor Welder Inverter
Power line
L
N
PE
Figure. Conductive noise entry route