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.