By pressing the piezo element, enough energy is generated to start up a microcontroller, take a measurement and show the result on the e-ink display. The energy consumption for the whole system is very low (less than 30 uJ). The measurement is displayed until a new activity is started by pressing the piezo key.

The piezo element we use is provided by the firm Algra. It is low-cost, noiseless and can support millions of cycles.