Hioki BT4560 - Appx. 2 Four-Terminal Pair Method

A2
Four-terminal Pair Method
Appx. 2 Four-terminal Pair Method
This instrument uses the four-terminal pair method as the measurement method.
In addition to the characteristics of the AC four-terminal method, which is unaffected by the contact
resistance, this is a more accurate method that is unaffected by the magnetic eld caused by the
measuring current.
The principles of the AC four-terminal method and the four-terminal pair method are described
below.
AC four-terminal method
R
1
R
2
R
3
R
4
Measuring
object
V
A
SOURCE-H
SOURCE-L
SENSE-H
SENSE-L
Ammeter
Current
source
Voltmeter
R
1
to R
4
: Resistances of measurement probes and contact resistances of contact portions
This method is unaffected by the wiring resistance of the measurement probes and the contact resistance
between the measurement probe and the object being measured, and is suitable for low resistance
measurement. This method uses the measuring current between the SOURCE terminals to measure the
voltage of the object being measured at the SENSE terminals.
The current owing through the voltmeter can be ignored because of the voltmeter’s high impedance. The
voltage actually generated in the object being measured can thus be measured because the voltage drops due
to the resistance of the wiring and the resistance of contact can be ignored even if there is wiring resistance or
contact resistance in the portions corresponding to
R
2
and R
3
.
Four-terminal pair method
Measuring
object
SOURCE-H
SOURCE-L
SENSE-L
SENSE-H
V
A
Current
source
Ammeter
Voltmeter
Measuring
object
V
A
SOURCE-H
SENSE-H
SENSE-L
SOURCE-L
The AC four-terminal method is suitable for a low resistance measurement because it is affected by the
resistance of the wiring and the contact resistance. The magnetic eld of the measuring current produces an
induced electromotive force that affects the SENSE terminals.