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Loading Errors (ac volts)
In the ac voltage function, the input of the Agilent 34401A appears as a
1 M
Ω resistance in parallel with 100 pF of capacitance. The cabling that
you use to connect signals to the multimeter will also add additional
capacitance and loading. The table below shows the multimeter’s
approximate input resistance at various frequencies.
For low frequencies:
Error
(%) =
− 100 x R
s
R
s
+ 1 MΩ
Additional error for high frequencies:
Input Frequency
100 Hz
1 kHz
10 kHz
100 kHz
Input Resistance
1 MΩ
850 k
Ω
160 kΩ
16 kΩ
Error (%) = 100 x
é
ê
ë
ê
ê
1
1 + ( 2 π x F x R
s
x C
in
)
2
− 1
ù
ú
û
ú
ú
R
s
= source resistance
F = input frequency
C
in
= input capacitance (100 pF) plus cable capacitance
√
7
Chapter 7 Measurement Tutorial
Loading Errors (ac volts)
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