Keysight U2741A Guide D'utilisation page 59

Other Sources of Measurement Error
Loading errors (AC volts)
In the AC voltage function, the input of the digital multimeter appears as a 1 MΩ
resistance in parallel with 100 pF of capacitance. The cabling that you use to
connect signals to the digital multimeter also adds capacitance and loading.
For low frequencies, the loading error is
Error %
At high frequencies, the additional loading error is
Error %
R
F = Input frequency
C
Measurements below full scale
You can make the most accurate AC measurements when the digital multimeter is
at or near the full scale of the selected range. Autoranging occurs at 10%
(down-range) and 120% (up-range) of full scale. This enables you to measure
some inputs at full scale on one range and 10% of full scale on the next higher
range. In general, the accuracy is better on the lower range; for the highest
accuracy, select the lowest manual range possible for the measurement.
High-voltage self-heating errors
If you apply more than 300 Vrms, self-heating occurs in the digital multimeter's
internal signal-conditioning components. These errors are included in the digital
multimeter's specifications.
Temperature changes inside the digital multimeter due to self-heating may cause
additional error on other AC voltage ranges.
Keysight U2741A User's Guide
100 × R
–
= - - - - - - - - - - - - - - - - - - - -
( )
R + 1 MΩ
s
= 100 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1
( ) ×
= Source resistance
s
= Input capacitance (100 pF) plus cable capacitance
in
(Equation
s
1
1 + ( 2π × F × R × C
s
in
Measurement Tutorial
2):
(Equation 3):
–
)
3
(2)
(3)
59