Alan built a reciprocal frequency counter. What sets reciprocal counters apart is that they adjust to the signal measured, sort of an auto-ranging feature.
It is AVR based and automatically enables or disables a prescaler to handle frequencies from 0.5 Hz to 100 MHz. It can give the same precision whether the signal is fast or slow…
[I have a] question about the front end. I’ve tried various input circuits, I’ve tried biasing inverters, schottky inverters, etc. I want the input to support even measuring mains voltages if possible.
Any suggestions for Alan?