When using a 0.2mm pitch pin lead: 1.1mΩ
When using a 0.5mm pitch pin lead: 0.92-0.97mΩ
When using a 9287-10 Clip Type Lead: 0.85-0.95Ω
This is caused not by contact resistance between the probe and the subject of measurement but by
current distribution in the subject of measurement but by current distribution in the subject of
measurement.
Image 1 is an example of a plot of the equipotential lines of a metal plate. Just like the relationship
between wind and the barometric charts used in weather forecasts, current density is higher where
the equipotential lines are close to each other and lower where the lines are farther apart. The
image shows that the potential gradient is greater near the sources of current. This is because these
points are where the electric current is in the middle of spreading across the metal plate, leading to
higher current density. For this reason, when a terminal for detecting voltage is placed near one of
these sources of current, just the slightest change in contact position can lead to major variation in
measured values. Use of Hioki’s 9453 four-terminal lead or a similar lead to detect voltage on the
inner side of the sources of current is desirable to avoid these effects. In other words, if
measurement is conducted within the width (W) or thickness (t) of the subject of measurement,
current distribution is likely to be stable.
A plot of the equipotential lines of metal plate showing current distribution at 50µV intervals when
applying a 1A current at the endpoints of the plate (300 (W) x 370 (L) x 0.4 (t).
As shown in image 2, it is desirable to locate the sensor terminals within the plate’s W or t value of
the sense terminals:
Probing locations when the subject of measurement has width and thickness values.
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