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. * 1 year warranty.