4263B
Four-T
erminal P
air Conguration
The
4263B
uses
the
four-terminal pair
measurement conguration
which permits
easy,
stable,
and
accurate
measurements
and
avoids the
measurement limitations
due to
factors such
as
mutual
inductance
,
interference
of the
measurement signals
,and
unwanted residual
in the
test
connections
.
Figure
7-4
shows
the
four-terminal pair
measurement principle
. The
UNKNOWN terminals
consists
of
four
coaxial
connectors.
H
CUR
:
High
current
H
POT
:
High
potential
L
POT
:
Low
potential
L
CUR
: Low
current
Figure 7-4. F
our-Terminal P
air Measurement Principle
The four-terminal pair measurement method has the advantage in both low
and high
impedance measurements
. The outer shield conductors work as the return path for the
measurement signal current (they are not grounded). The same current ows through both the
center conductors and outer shield conductors (in opposite directions), so no external magnetic
elds are generated around the conductors (the magnetic elds produced by the inner and
outer currents completely cancel each other). Therefore, test leads do not contribute additional
errors due to self or mutual inductance between the individual leads.
7-6 Impedance Measurement Basics
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