HM Digital PH-200 Water pH Testing Meter. Waterproof. Measure 0-14 pH. Temperature Tester, IP-67 rating, Factory Calibrated, ideal for all pH testing, water purification applications, wastewater regulation, aquaculture, hydroponics, colloidal silver, labs and scientific testing, pools and spas, ecology testing, boilers and cooling towers, water treatment, wine, coffee, agriculture and more.