We soldered together a simple circuit to measure the AC grid frequency. It does this using a low-cost microprocessor to time the interval between each change in direction of electric current from a normal power socket.

The circuit is connected via an interface board to a web-linked computer which takes a reading of the grid frequency every second. The computer passes this value to a script on our web server where it is then saved.

On your browser is a Flash movie which has been programmed to regularly download the current value from the web server and move the needle-graphic accordingly.

The needle should move most of the time. If it stays still, or goes off the scale, there's probably a fault at our end, so try later.