Waterproof tester, 3 ranges: 0 – 199.9 ppm, 200 – 1999 ppm and 2.00 – 10.00 ppt, resolution 0.1 ppm, 1 ppm and 0.01 ppt, microprocessor controlled, large display with simultaneous temperature display, automatic temperature compensation (ATC), 3 point calibration, user-replaceable sensor.