[Wolf] sent in this site a while back, and I thought that this frequency meter how-to looked pretty useful. It’s based on an Atmel AT89C52 and a gutted multi-meter. The circuit isn’t too bad. (The worst of it has to be all the display lines.) The Atmel grabs the signal to be measured and drives the display, so the parts count is pretty low.
DIY Frequency meter
July 29, 2007 By 9 Comments