Requirements for Kelvin Points
Each 4-Wire measurement requires two Kelvin pairs, one at each end. Place Kelvin pairs as
close to the device-under-test as possible. WHY? The 4-Wire Test measures from Kelvin pair
to Kelvin pair, so any contact and lead resistance between the Kelvin pairs is added to the
resistance measurement of the device-under-test.
Examples of how Kelvin pairs placement affects 4-wire measurement:
DUT #1: The measurement is only of the device-under-
test. This is the ideal, but in real-world situations it may be
nearly impossible to achieve.
DUT #2: The measurement includes part of the fixture.
Warning! If a lot of the fixture is between a Kelvin Point
and the device-under-test, the 4-Wire Test will be
considerably compromised.
DUT #3: The measurement tests only part of the device-
under-test. For example, by using probe pins, you can
eliminate the resistance of a connector from the
measurement.
Visible and Hidden Point Mates
Unlike conventional fixtures that require two wires per measurement, 4-Wire fixtures
require four wires in two pairs per measurement. In order to fixture four-wire to the
CH2, the two wires in each 4-Wire Pair must connect to two different kinds of test
points called Visible and Hidden. Each Visible point has one specific Hidden mate and
the two must go together.
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