Hioki DSM-8104, Instruction Manual

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6.2.4 Measurement of circuits
The circuit is a combination of plural parts. Insulation resistance is measured outside of
circuits such as between circuits that are mutually insulated and between a circuit and
casing. The measuring method and handling of this meter are the same as those used
in measurement of insulation resistance of parts.
Normally, measuring voltage higher than voltage that is used inside the circuit is used in
measurements of insulation resistances of circuits. Measurement must be made
exercising reasonable caution so as not to affect circuits such as measuring voltage and
polarity.
When measuring samples such as a telephone cable that has many points of
measurement, it is effective to measure utilizing features of this meter, such as
measuring by automatically changing measurement points and making measuring
conditions identical.
6.3 Measuring Planar Sample
When measuring insulation resistance of a sample that has no terminals, devices that act
as terminals must be installed on the sample in one form or the other.
Devices of various shapes that act as terminals can be considered. Convenience with
which to easily exchange samples is desirable and devices of a structure that become
terminals only by contacting a sample are used more.
Terminals for measurement must be free of malcontact and must contact the sample
tightly. However, the shape and structure of the terminal differ depending on the
sample shape and property. Various methods to measure insulation resistance are used
with solid-state insulating materials by having a terminal (electrode) with a smooth and
flat surface contact a sample of a pin type with a specified shape or smooth and flat
surface so that contact can be made tightly without a gap.
This section describes these measuring methods.
6.3.1 Measurement by pin terminal
Insulation resistance is divided into “volume resistivity” caused by a current that flows
inside a sample and “surface resistivity” caused by a current that runs the surfaces of a
sample. Insulation resistance measurement is measurement of volume and surface
resistivities.
For example, a measuring terminal is made using a planar sample, by drilling two holes
of a specified diameter, such as tapered holes, at a predetermined spacing, and by
inserting pins coated with a material with relatively low insulation resistance such as
vaseline.
The surfaces of samples do not have to be finished into smooth surfaces and these
terminals can achieve relatively stable contact with a simple structure.
Set the measuring mode to “resistance measurement.”