The Oakton WD-35634-54 ORPTestr 5 pocket-sized OPR tester has a replaceable single-junction sensor which can be easily switched out, allowing you to save money by using the tester body over and over again. A large LCD makes viewing measurements easy and features a three-color backlight indicating operational mode - blue for measurement, green for calibration and red for alarm condition. It is ideal for checking dirty water, heavy metals, sulfides, and organic materials.

Additional features include a hold function to lock in measurements, self-diagnostic error message, and status icons for measurement stability and low battery voltage. The IP67-rated housing features an easy-to-grip design and floats if accidentally dropped in water when sensor cap is on. Powered by 4 AAA batteries, the testers can operate up to 400 hours continuously. To conserve power, the unit will auto power-off after 8 minutes of non-use.