Beat Frequency Measurement


I am working on a project that requires me to measure the beat frequency of a signal with an Arduino.

In my project, I plan on having two 32k crystal oscillators (a measurement crystal and a reference crystal) that will be beat together through a adder op-amp circuit. The output of the op-amp will have the high frequency of the oscillators plus a low frequency beat of the differences in their frequencies. I want to measure the frequency of this beat.

I don't think the arduino is quite fast enough to just measure the frequencies right off of the crystals, that's why thought of the beat frequency idea.

I have two putative solutions, but was looking for some additional input/ideas/feasibility.

1) Run the beat frequency through a low-pass filter to try and only get the beat frequency, then go through a schmitt trigger to get nice clean 0-5 Vdc input for my Arduino.

2) Forget the whole beat-frequency idea and use frequency dividers, then just measure the output of those.

Any input on this idea?



You are greatly underestimate arduino, it's capable to count 7 MHz: