Measures dissolved oxygen to determine water quality in environmental testing, labs, industrial and municipal waste water, aquariums and fish hatcheries. Designed for simple one-hand operation with automatic temperature compensation and calibration to air. The polarographic probe has a built in temperature sensor and easy-to-replace pop-off probe heads. Simultaneously displays dissolved oxygen and temperature readings. Also holds readings and recalls minimum and maximum. IP67 waterproof, floats if accidentally dropped in water. Comes ready to use in a soft carrying case with belt loop, two spare probe heads, electrolyte and 4 AAA batteries.