Gardeners can easily measure and maintain nutrient strength levels with the waterproof Truncheon from Bluelab. Truncheon reads in EC (0.2-3.6), CF (2-36), and TDS in both 500 and 700 ppm scales (100-2520). Accurate within ± 4% of reading with a resolution of .1 EC, the Truncheon runs on three AA alkaline batteries and comes with a five-year manufacturer's guarantee.