Hardware Request: Frequency Counter

I’d be interested to know if anyone has built or is planning to build a mains supply frequency counter with an accuracy of around 0.001 Hz. Real time monitoring of the supply frequency shows the instantaneous demand/supply balance on the grid of course, so would need to have a way to report this in real time. Also wondering whether it could be a useful data dimension for appliance profiling. Interested in any pointers to projects or other information on this.

Yes, it’s been done. I believe “EmonLib Pro” by @nchaveiro will do it, and I know Martin Roberts’ energy diverter can also do it. MartinR’s PLL is under Resources > Building Blocks (Energy Diversion).

Thanks very much for quick response - will take a look!