In article
,
harry wrote:
Even a 4 quid multimeter will have an input impedance in the mega Ohm
range. The inaccuracies due the the meter impedance and measurement
leads is vanishingly small and completely swamped by the specified
accuracy of the shunt resistor and voltmeter.

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mailto:news{at}admac(dot}myzen{dot}co{dot}uk

Depends on what you are trying to measure.

If it is the voltage in an electronic device, it may draw more current
than the device.
If it was a washing machine, then neither here nor there.

You have to understand the limitations of your equipment.

In the days when moving coil meters were the norm, allowance had to be
made for the loading of the meter on the measurement. If this was a
problem, you'd use a valve voltmeter with a high input impedance - an
expensive device. Modern DVMs have a similar high input impedance for
pennies. And in general don't need an any allowance made when measuring.

What is more of a problem in practice is a high impedance meter will read
mains voltages where there is no actual connection - caused by
capacitive/inductive coupling. A moving coil meter which draws more
current shows near zero.

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*Why is a boxing ring square?

Dave Plowman London SW
To e-mail, change noise into sound.