Description Bluelab Truncheon Nutrient Meter Main Features EC (0.2 – 3.6), CF (2 – 36) and ppm scales (TDS and 700 scale) Fully waterproof No calibration required Auto sense on and off No external switches or adjustable buttons Battery life minimum 1 year (or shelf life of battery) 5 Year Bluelab Guarantee     May be effected by electricity in your water, remove a small portion of your water from reservoir to be tested. Clean electrodes often, salt build-up may affect your results. May need calibration occasionally.