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.
Where:
Vs = Ideal DUT voltage
Rs = DUT source resistance
Ri = Input resistance (10 MΩ or >10 GΩ)
Error (%) = −100 x Rs
Rs + Ri
To minimize loading errors, set the DMM’s dc input resistance to
greater than 10 GΩ when needed (for more information on dc input
resistance, see page 113).
VS
RS
HI
LO
RiDMM
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Chapter 8 Tutorial
Measurement Fundamentals
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