Keysight 34972A - Sources of Error in DC Current Measurements; Sources of Error in AC Current Measurements

Tutorial 7
Keysight 34970A/34972A User’s Guide 303
Sources of Error in DC Current Measurements
When you connect the internal DMM in series with a test circuit to measure
current, a measurement error is introduced. The error is caused by the DMM’s
series burden voltage. A voltage is developed across the wiring resistance and
current shunt resistance of the internal DMM as shown below.
V
s
= Source voltage
R
s
= Source resistance
V
b
= Burden voltage
R = Current shunt resistance
Error (%) =
Sources of Error in AC Current Measurements
Burden voltage errors, which apply to DC current, also apply to AC current
measurements. However, the burden voltage for AC current is larger due to the
internal DMM’s series inductance and the measurement connections. The burden
voltage increases as the input frequency increases. Some circuits may oscillate
when performing current measurements due to the internal DMM’s series
inductance and the measurement connections.
V
s
R
s
V
b
R
DMM
100%– V
b
×
V
s
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