HM Digital COM100 Water Quality Testing Meter. Waterproof. Measure EC/TDS. Temperature Tester. IP-67 rating. Factory Calibrated. Ideal for all water quality testing, water purification applications, wastewater regulation, aquaculture, hydroponics, colloidal silver, labs & scientific testing, pools & spas, ecology testing, boilers & cooling towers, water treatment and more. The COM-100 is a professional level EC/TDS meter at an unbeatable price.