4-in-1 Digital Water Quality Meter Extech EX900 is a portable, handheld instrument for measuring multiple water quality parameters in one unit. A water quality meter uses interchangeable flat surface electrodes (for chlorine, pH, ORP) that allow the meter to make direct surface contact measurements.4-in-1 water tester measures: Chlorine, pH, ORP, Temperature. This multi-parameter water tester is designed to work effectively in liquids, semi-solids, and solids. portable water quality meter features a large 3 1⁄2-digit (2000 count) digital display with bar graph for clear readings, along with an automatic electronic self-calibration function for chlorine and ORP measurements. Applications:- Pool/spa water maintenance, municipal water sampling, wastewater testing, aquaculture, and environmental field monitoring etc.