Waterproof PPM Pocket Tester From Bluelab
The Bluelab ppm Pen measures conductivity and temperature and is a great way to ensure plants are receiving the proper amounts of nutrients. This pen features a backlit LCD display, optional calibration and a successful calibration indicator, a hold function, low battery warning, auto off function, automatic temperature compensation, and is fully waterproof. It operates in units of 500 or 700 ppm and has a range of 0-5000 ppm or 0-7000 ppm, and accuracy to 50ppm or 70ppm. Requires one AAA battery (not included) and has a 12 month manufacturers warranty.