This revolutionary EC meter is powered by a magnet instead of a battery! A gentle shaking action generates the energy to power this simple, yet sophisticated meter. With just a few easy steps you will get a quick & accurate reading of the electrical conductivity (EC) of your nutrient solution. This patented meter will completely simplify your growing experience and success. Green LED display. No batteries required. Factory calibrated. Automatic temperature compensation. Automatic on/off function. Waterproof.