4-Wire Measurements; 4-Wire High Resistance Measurements - Fluke 8508A User Manual

4-wire Measurements

With a 4-wire connection the lead resistances have negligible effect and only the value of
Rx is displayed.

4-wire High Resistance Measurements

When making very high resistance measurements above about 1 M , a metal screen can
be wrapped around the resistor to reduce noise, usually caused by charge injection.
Connecting the
parallel with the unknown resistor). The resistor under test should not be grounded, as
this will make the measurement noisier.
SENSE HI
SENSE LO
INPUT HI
INPUT LO
GUARD
Figure 3-5. 2-Wire Measurements
INPUT HI
SENSE HI
GUARD
SENSE LO
INPUT LO
Figure 3-6. 4-Wire Measurements
terminal to the screen will intercept leakage via the screen (in
GUARD
INPUT HI
GUARD
GUARD
INPUT LO
Figure 3-7. 4-Wire High Resistance Measurements
Using the Measurement Functions
INPUT HI
Rx
INPUT LO
INPUT HI
SENSE HI
Rx
SENSE LO INPUT LO
Metal
Screen
SENSE HI INPUT HI
Rx
SENSE LO INPUT LO
Making Measurements
adj091f.eps
adj092f.eps
adj093f.eps
3
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