Errors in High Resistance Measurements
When you are measuring large resistances, significant erro rs can occur
due to insulation resistance and surface cleanliness. You should take
the necessary precautions to maintain a “clean” high-resistance system.
Test leads and fixtures are susceptible to leakage due to moisture
absorption in insulating materials and “dirty” surface films. Nylon and
PVC are relatively poor insulators (109 ohms) when compared to PTFE
Teflonâ insulators (1013 ohms). Leakage from nylon or PVC insulators
can easily contribute a 0.1% error when measuring a 1 MΩ resistan c e in
humid conditions.
DC Current Measurement Errors
When you connect the multimeter in series with a test circuit to
measure current, a measurement error is introd uce d. The error is
caused by the multimeter’s series burden voltage. A voltage is developed
across the wiring resistance a nd current shunt resistance of the
multimeter as shown below.
Teflon is a registered trademark of E.I. duPont deNemours an d C o.
Ideal
Meter
Vs
I
LO
Rs
RVb
Vs = source voltage
Rs = DUT source resistance
Vb = multimeter burden voltage
R = multimeter current sh unt
Error ( % ) = −100% x Vb
Vs 7
Chapter 7 Measurement Tutorial
Errors in High Resistance Measurements
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