RadioBanter - View Single Post - inexpensive analog audio pitch (frequency?) meter or schematic/ plans for one?

Richard Crowley[_2_] · January 8th 08, 01:46 AM posted to rec.radio.amateur.homebrew

"Fred McKenzie" wrote...
In article
,
wrote:

I just want to do analog metering
with moving needle meters.

MS-

I once had an automotive tachometer that hooked between the engine's
points and ground, and was calibrated in RPM. I do not recall, but
there may have been separate scales for 6 and 8 cylinders.

I don't think it had any active components, and didn't require an
external power supply. It was measuring frequency by clipping,
differentiating the waveform and reading the integral of the pulse on a
sensitive meter movement. It was calibrated from a 60 Hz sine wave.

You may find something similar (or one with active circuits) if you
search for analog tachometer circuit on the web. If you have an old
automotive tachometer, just trace out its circuit.

Using it for higher audio frequencies should be a matter of calibration.

If you differentiate the signal enough for the range of 20-20KHz,
you end up with an indication indistinguishable from "volume"! :-)
The request is fundamentally absurd.