Hioki DSM-8542, Инструкция по эксплуатации, Страница: 67 / 140

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6.1.2 Connecting
measuring terminals
Insulation resistance is measured by connecting a sample between the “INPUT” and
“OUTPUT” terminals. Insulated cable with sufficient withstand voltage to measuring
voltage can be used between the “OUTPUT” terminal and sample terminal. However,
use measuring cable with a guard (shielded-conductor cable with a densely braided
shielding braid) between the “INPUT” terminal and sample terminal. Be certain to
connect the outer conductor (shielding braid) to the outer electrode of the “INPUT”
terminal.
[Notice]
Noise that is generated by the measuring cable sometimes hampers stable
measurement of high resistance.
Use a low-noise shielded-conductor cable meeting the specification of
HIOKI as a cable connected between the “INPUT” terminal and sample for
stable measurement.
6.2 Measuring Parts, Circuits and Other Items
Measurement is taken by setting the mode to the “Resistance Measurement” mode
referring to 5.2.2 “Setting measuring mode.”
Automatic measurement using a jig is effective when measuring parts and circuits of the
same shapes in a large quantity or with many points of measurement. A holder or a jig
for measurement is needed when measuring very small samples.
If shapes of parts and circuits are not uniform, when shapes or weights are large, or
when fewer samples are measured, more measurements are made without using a holder
or a jig for measurement.
6.2.1 Using
measuring jigs
Efficient measurement can be made if a measuring jig or holder is used when there are
many parts to be measured or there are many points of measurement such as circuits.
Generally speaking, insulation resistance is measured by measuring a current that flows
through a sample and flows from one terminal to a terminal on the other side and by
converting the current into a resistance value.
To measure only a current that flows through a sample, a current that does not pass
through the sample, such as a current flowing through an insulating material of a sample
holder, must be escaped to the “GUARD” terminal (The outer side of the “INPUT”
terminal plays this role with the “GUARD” terminal.) to prevent a current from entering
the “INPUT” terminal
The “GUARD” terminal is the common side of the current measuring unit. The terminal
absorbs a leakage current that flows in the sample holder, jig or other parts, to eliminate
impacts of current measurement inside the sample. The outer electrode of the “INPUT”
terminal or the “VOLTAGE INPUT” connector plays the role of the “GUARD” terminal.
The electrical polarity of the “GUARD” terminal is “-.”
“Guarding” means directly flowing currents, which are not measured, to the common
side to prevent them from entering the “INPUT” terminal.