Hioki DM7275 Series - Appx. 5 Self-Calibration

Appx.11
Self-calibration
An effective approach for dealing with conductive noise is to implement countermeasures while
monitoring the results with the Hioki 3145 Noise HiLogger. Once the offending circuit has been
identied, the countermeasures depicted in Figure 2 provide an effective way to address the issue.
L
N
PE
L
N
PE
Instrument
Power lines
Separate circuit’s power lines
Isolation
Isolation
Common-modelter
on ingress circuit
Physicalseparationofpowerlines
Externaldevice
(computer,
programmable
controller)
Figure 2. Conductive Noise Countermeasures
Physicallyseparatingpowerlines
It is desirable that powered devices, welders, and similar equipment be connected to a power
supply on a separate circuit than the instrument.
Insertingacommon-modelter(EMIchoke)intotheingresscircuit
For maximum effectiveness, choose a common-mode lter with high impedance. The more lters
are added, the more effective this measure will be.
Isolation
Photoisolation of control lines is an effective noise countermeasure. It is also effective to isolate
power lines with a noise-suppressing transformer. Please note that use of a common ground line
across the isolation will reduce the effectiveness of this approach.
Appx.5 Self-calibration
The instrument’s self-calibration function serves to maintain measurement precision by correcting
for uctuations in the internal measurement circuitry. The instrument is designed for automatic self-
calibration.
Specic operation depends on the measurement state (p. 37)
RUN state
Self-calibration is performed between measurements.
STOP state and
when using
the
EXTERNAL
trigger source
Self-calibration is performed continuously while waiting for a trigger. When a trigger
is input, self-calibration stops, and measurement starts. Once measurement is
complete, self-calibration resumes.
If the trigger function’s “number of measurements” parameter is set to a value other
than 1, self-calibration will resume after the set number of measurements has been
performed.
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Appx.
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