Hioki BT3554-50, Инструкция по эксплуатации, Страница: 169 / 188

155
AC Four-Terminal Method Measurement
11.3 AC Four-Terminal Method
Measurement
The instrument uses the AC four-terminal method for resistance
measurement to cancel out wire resistance of the test lead and
contact resistance between the test lead and the object under
measurement. The following figure shows the principle of the AC
four-terminal measurement method.
Constant-
current source
DC-
elimination
capacitor
R
1
R
2
V
IS
R
3
R
4
I
S
Resistance measurement circuit
R
1
to R
4
:
Wire resistance value
of test lead and contact
resistance at contacts
Voltmeter
Resistance
R
The instrument applies the AC current I
S
from the instrument’s
SOURCE terminals to the object under measurement. The voltage
drop V
IS
, due to the impedance of the object under measurement,
is measured across the SENSE terminals. At this time, the SENSE
terminals connects to the internal high-impedance voltmeter.
Thus, little current flows through the resistances R
2
and R
3
, a wire
resistance and a contact resistance, respectively. As a result,
little voltage drops across the resistances R
2
and R
3
. In this way,
the voltage drop due to the resistances R
2
and R
3
is canceled
out. The instrument uses synchronous detection to separate the
internal impedance of the object under measurement into effective
resistance and reactance and displays the effective resistance
alone.
HIOKI BT3554F961-00 HIOKI BT3554F961-00