What is it

MAFM103 ('Mains AC Frequency Meter 103') is a device that measures the frequency of the electric grid. It uses a novel approach to calculate the frequency from samples and is thus fast and accurate: 50 measurements per second at a standard deviation of 0.1 milliHertz. It transmits its measured values via a serial interface.

It is designed for 50Hz grids.

Why did you make it?

I was interested in calculating the exact frequency of a sine wave from sampled data. Accuracy should be well above 'counting zero crosses'. I rediscovered an old but very powerful algorithm. And I adapted it to the measurement of the 50Hz sine at my home socket. It was fun to compare it against the reported european grid frequencies.

What makes it special?

It is fast.

It is accurate.

And you can hook it up to any computer and generate high resolution recordings of the grid frequency.