[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik, Kaashoek)

[Stephen C. Menasian]

On Tue, 12 Jul 2022 08:17:33 -0800
Bob kb8tq via time-nuts <time-nuts at lists.febo.com> wrote:

> Hi
> 
> If you have any ceramic capacitors in the mix, they are often
> microphonic. The X7R versions are typically the best “high C” types.
> NPO’s normally are completely non-microphonic. Other non-ceramic caps
> should be ok, but who knows. 
> 
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Actually X7Rs are quite bad. Z5Us, also. Both are piezoelectric. I don't
use them any more except for power supply bypass in non-critical
supplies. As a part of a precision temperature controller project
(microKelvin), I needed to select capacitors for low microphonics.
The ceramic types mentioned above are the worst offenders; but
several other types (certain film types included) show some microphonic
activity.

Best to evaluate every capacitor type by charging to 10 Volts, or so, AC
coupling to an audio amplifier/sensitive oscilloscope/or other and tapping
to see if noise is produced.

Stephen Menasian