Oxidation reduction potential (also known as redox potential, oxidation / oxidation potential, or ORP) is a measure of water's ability to gain or lose electrons in chemical reactions. Just as the transfer of hydrogen ions in water determines the pH level, the transfer of electrons in water determines the ORP value.

Specifications:

• Measures oxidation reduction potential (redox) and temperature
• Auto-ranging calibration with digital fine tuning
• Includes 4 pH buffer solution in a sponge embedded in a clear cap, so you can see if it's dried up
• Waterproof housing
• Simultaneous temperature display
• Measurement range: -999 to +1000 mV
• Digital calibration (push button)
• Auto-off function, data-hold function and low-battery indicator.
• Display: large and easy-to-read LCD screen includes simultaneous temperature reading.
• Factory calibrated: the ORP-200 meter is factory calibrated to +200 mV. The meter can be easily recalibrated with digital calibration using the push buttons, rather than a screwdriver.
• Includes a cap, batteries, and lanyard

NOTE: The ORP value of a water supply is directly related to the effect it has on plumbing and bacteria growth. The life expectancy of bacteria in water is more dependent on the ORP value than the chlorine concentration or pH value. For swimming pools with a pH value around 7.5, the ORP value must be kept above 700mV to kill harmful bacteria.
The ORP-200 meter is ideal for all ORP testing, including anti-oxidant measurement, water purification applications, ionizers, agriculture, aquariums and aquaculture, chlorine monitoring, cooling tower disinfection, environmental testing, fruit and vegetable washing, hydroponics, metal finishing, ozone system monitoring, pharmaceutical and medical applications, pools and spas, pulp bleaching, vineyards and wineries and water treatment.