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FLUKE 87V High Z mode input Impedance value
bdunham7:
It isn't really helpful to think about the input characteristics of a Hi-Z meter like this in ohms. The small current going through the meter and how it responds to applied voltage depends on a number of characteristics put together--the input capacitance, the leakage of the protection clamps and the bias current of the input circuit, etc. The bias current may be more or less constant, the leakage current will depend strongly and non-linearly on input voltage and in the case of a non-steady voltage, the current through the capacitor will depend on how the voltage is changing.
In cases where all of that is so small that it doesn't matter, then things are great. If you start trying to use a Hi-Z voltmeter to look at G-ohm voltage dividers or circuits with picoamps of current, you'll discover all of what I just said above to be true.
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