The Bluelab Conductivity Pen is a highly accurate, well built piece of essential equipment for growing in hydroponic systems. As well as displaying an EC reading, it will also show you the temperature of your solution. General Information Ensuring your EC level is within correct range is essential for healthy, vigorous plant growth. It will help you identify whether you are over or underfeeding your plants which ultimately gives you more control of the grow cycle. Benefits Measures conductivity and temperature Selectable units for conductivity and temperature Backlit LCD display Calibration optional Successful EC or ppm calibration indicator Hold reading function Low battery indicator Fully waterproof Auto off function Automatic temperature compensation 1 x AAA alkaline battery included