What is ORP?

Oxidation-reduction potential (ORP), commonly referred to as REDOX, is a measure in millivolts of the tendency of a chemical substance to oxidize or reduce another chemical substance.

Oxidation is the loss of electrons by an atom or ion. Reduction is the net gain of electrons by an atom or ion.

Accurate ORP Sensor

How is ORP Measured?

ORP is measured using an electrochemical ORP (REDOX) sensor. Very similar to a pH sensor, the ORP sensor is normally combination type which contains a measuring electrode and reference electrode.

The measuring cell, which is typically a noble metal such as platinum or gold, detects changes in REDOX potential and the reference provides a stable comparison signal. ORP is expressed in millivolts and typically a pH instrument using the mV scale is used to display the readings.


Why is ORP Measurement Necessary?

ORP measurements are a cost effective method to control various processes. Effective disinfection using chlorine, ozone, or bromine are very common uses. It is also used in in process applications to control destruction of chromate or cyanide, as well as bleach production and wet scrubbers.

Common Applications:

  • Prechlorination and dechlorination in water/wastewater treatment
  • Cyanide destruction and chromate reduction in metal finishing
  • Ozone treatment process control
  • Bleach production
  • Poultry processing
  • Fruit and vegetable washing
  • Pulp bleaching
  • Chlorine addition in commercial swimming pools & spas