Before diving into direct measurement, I first explored the possibility of using an online service that provides the mains frequency (50 Hz in Europe) in real time.

There are indeed a few websites that publish this information — mostly in Germany and Switzerland — but:

• some only offer limited-time access,

• others don’t provide any public API,

• and most of them introduce several seconds or even minutes of delay, making the data unsuitable for true real-time use.

In short: it’s nearly impossible to find a reliable, open, real-time source for the 50 Hz mains frequency in France or across Europe.

👉 So, I decided to measure the mains frequency myself, using a local reference signal — a more independent and definitely more maker-style approach!

The next log will describe the measurement principle and the hardware setup in detail.