Oscilloscopes are great for visualising signals in electronic circuits. Their performance is usually measured in bandwidth and - now that analog oscilloscopes have almost completely disappeared - sampling rate, the higher the better. Scopes like that allow the user to capture extremely fast signals, but what if you want to measure a very slow signal?

A battery discharge curve is an example of a really slow signal. If you want to measure it, you need an oscilloscope with a timebase of hours per div instead of mere seconds. This project (posted on the Elektor Labs website) is based on an Arduino Mega 2560 board with a custom add-on shield. It allows you to do just that by expanding the oscilloscope's tracking time up to twelve hours or more. As a bonus all parameters are displayed on the oscilloscope screen. Of course the shield works on good old analog oscilloscopes as well.