Hioki 3554, Instruction Manual

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147
10.3 AC Four-terminal Method
索引
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The instrument uses the AC four-terminal method, so that resis-
tance measurement can be carried out with the resistance of the
leads and the contact resistance between the leads and the
object to be measured canceled out. The following figure shows
the principle of the AC four-terminal measurement method.
An AC current (I
s
) is supplied from the SOURCE terminals of the
instrument across the tested battery. The voltage drop across
the internal impedance of the battery (V
IS
) is measured by the
SENSE terminals. At this point, since the SENSE terminals are
connected to an internal voltmeter with a high impedance,
almost no current flows through the resistances R
2
and R
3
which
represent the lead resistances and contact resistances. As a
result, there is almost no voltage drop across the resistances R
2
and R
3
. Thus the voltage drop due to the lead resistances and
contact resistances is very small, and these can be canceled
out. In the instrument, a synchronized wave detection system is
used, whereby the internal impedance is separated into resis-
tance and reactance, and the resistive component only dis-
played.
10.3 AC Four-terminal Method
Resistance measurement circuit
Voltmeter
Resistance
I
s
R
1
R
2
V
IS
R
3
R
4
Values R
1
to R
4
are the resistances of the test leads plus contact resistances.
DC-elimination
capacitor
Constant current
source