I have measured electrolytic capacitors with my nano and they are woefully bad at high frequencies.? Now that I have acquired a nanoVNA that can go down to 10 kHz I plan to do some testing to see if they are just as bad at that frequency.
Bob
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On Sunday, February 14, 2021, 03:55:40 PM PST, Dragan Milivojevic <d.milivojevic@...> wrote:
That makes no sense whatsoever.
On Sun, 14 Feb 2021 at 23:14, Manfred Mornhinweg <manfred@...> wrote:
And what's the best bypass cap? Well, a single, plain, cheap aluminium
electrolytic!
Attached is the impedance plot for a 47?F, 25V electrolytic cap, measured
with lead lengths compatible with mounting it snugly on a PCB. Their narrow
pin spacing helps a lot in keeping their ESL low. I kept the same scale to
make comparison easy.
YES, a single 47?F electrolytic is a much better bypass cap than a
parallel combination of two ceramic caps of different values! Even in the
low VHF range!
The problems with electrolytic caps is that their ESR rises with age, and
rises much faster if they run hot, or if they have to carry large ripple
current. So they can't be applied in every situation. But in situations
that are kind to them, they are the cheapest and easiest way to get an
excellent wideband bypass.
