The discussion centers on the inability of a digital multimeter (DMM) to detect voltage or current when connected to a DC power supply or charged capacitor in an open circuit scenario. Participants highlight that multimeters measure current flow, which is absent in this case, contrasting it with antennas that can sense electrostatic forces despite being open circuits. The conversation emphasizes the importance of understanding the differences between steady-state (DC) and changing conditions (AC, step functions, pulses), and the role of sampling rates in measurement devices. Suggestions include using a digital storage oscilloscope (DSO) for better detection of transient spikes due to its higher sample rate.
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Because multimeters work on current flow and you are talking about an open circuit with zero current flow.thomasj said:
But an antenna also an open circuit and there is current in it.phinds said:
This is a good observation and shows the danger of confusing steady state conditions (DC) with changing ones (AC /Step Functions / Pulses). EM can't be dealt with with simple, one-line statements. Even JC Maxwell needed Three Equations!thomasj said:
Interesting but can you explain, please? I tried to use pulse DC with a push button but no effect.sophiecentaur said:
The title of your thread refers to Electrostatic Forces. When the forces are not Static, things are different. The reason that your DMM recorded nothing will be a combination of factors. Firstly, a Digital Analogue Converter (the heart of a DMM) takes samples and gets an average over its sample interval. The total charge that passes with an experiment like yours will depend on the Capacitance of the apparatus. The peak current could be fairly high (easily detectable by your DMM) but the average may be very small. It's the sort of thing that a 'clunky' analogue meter might show you by a tiny twitch of a needle. (Newer doesn't always mean better.thomasj said:
)Thanks, I suspect this. And if I would use a DSO instead? Sample rate of that device is high enough I guess. Shorter time period's average could be better here.sophiecentaur said:... but the average may be very small. It's the sort of thing that a 'clunky' analogue meter might show you by a tiny twitch of a needle. (Newer doesn't always mean better.
Depending on the capacitance of that wire, picoseconds or nanoseconds might be needed to see the spike.thomasj said:
The series R would be relevant, wouldn't it? RC time constant would be longeranorlunda said:
The way the OP stated it, is is the R of a short piece of wire.sophiecentaur said:
anorlunda said: