Errors In High Resistance Measurements; Dc Current Measurement Errors - HP 34401A User Manual

Chapter 7 Measurement Tutorial

Errors in High Resistance Measurements

Errors in High Resistance Measurements
When you are measuring large resistances, significant errors 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
are relatively poor insulators (10
PVC
13
Teflon insulators (10
can easily contribute a 0.1% error when measuring a 1 M resistance 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 introduced. The error is
caused by the multimeter's series burden voltage. A voltage is developed
across the wiring resistance and current shunt resistance of the
multimeter as shown below.
R
s
I
V
V
b
s
LO
V = source voltage
s
R = DUT source resistance
s
V = multimeter burden voltage
b
R = multimeter current shunt
Error %
Teflon is a registered trademark of E.I. duPont deNemours and Co.
9
ohms) when compared to
ohms). Leakage from nylon or
Ideal
R
Meter
100% x V
b
V
s
PTFE
insulators
PVC
7
205