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Chapter 8 Tutorial
Measurement Fundamentals
Loading Errors Due to Input Bias Current The semiconductor
devices used in the input circuits of the internal DMM have slight
leakage currents called bias currents. The effect of the input bias
current is a loading error at the internal DMM 's input terminals.
The leakage current will approximately double for every 10
temperature rise, thus making the problem much more apparent at
higher temperatures.
R
S
HI
V
S
LO
Where:
I
= DMM bias current
b
R
= DUT source resistance
s
R
= Input resistance (10 M or >10 G )
i
C
= DMM input capacitance
i
I
Error (V) =
x R
b
s
358
C
i
I
R
DMM
b
i
C
°
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