Agilent Technologies 34901A User Manual page 360

Chapter 8 Tutorial
Measurement Fundamentals
Loading Errors Due to Input Resistance Measurement loading
errors occur when the resistance of the device-under-test ( DUT ) is an
appreciable percentage of the instrument's own input resistance.
The diagram below shows this error source.
R
S
V
S
Where:
V = Ideal DUT voltage
s
R = DUT source resistance
s
R = Input resistance (10 M
i
−100 x R
Error (%) =
R
To minimize loading errors, set the DMM 's dc input resistance to
greater than 10 G
resistance, see page 113).
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HI
R
DMM
i
LO
Ω Ω
or >10 G )
s
+
R
s i
Ω
when needed (for more information on dc input
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