That's a tachometer. A lo pass filter, a comparator, a oneshot, a capacitor, and a meter on a trimpot. Every zero crossing, the comparator fires the oneshot, the cap integrates the pulses, and the meter shows the freq. Cal it with sine waves.... no harmonics.
Re: inexpensive analog audio pitch (frequency?) meter or schematic / plans for one?
Dec 31, 2007
2 Replies