Oxidation Reduction Potential (ORP)

What is ORP?

Oxidation reduction potential (ORP), also known as REDOX, is a measurement that reflects the ability of a molecule to oxidize or reduce another molecule:

  • Oxidation is the loss of electrons, so oxidizers accept electrons from other molecules
  • Reduction is the gain of electrons, so reducers donate electrons to other molecules

Oxidation reduction potential is measured as a single voltage in millivolts (mV). Oxidizers have a positive ORP value, while reducers have a negative ORP value.

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How is ORP Measured?

ORP is measured using an electrochemical sensor called an ORP or REDOX sensor. Similar to to pH sensors, the most common type of ORP sensor is a combination sensor with a measuring electrode and a reference electrode. The measuring cell, typically a noble metal like platinum or gold, detects changes in REDOX potential, while the reference provides a stable comparison signal.

Like a pH measurement, an ORP measurement is not a direct indicator of concentration, but rather an indicator of activity. However, in solutions with one active species, like pool water containing chlorine, ORP correlates to concentration.


Our extensive line of ORP products provide options for almost any application.

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Popular ProductsSensorex ORP Best Sellers

S272CD-ORP-MA and S272CD-ORP-MB – Smart ORP Sensors, Online Process

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TX105 – pH/ORP Transmitter, Loop Powered 4-20mA

Our TX105 is a fully-featured ORP/pH transmitter for use with pH and ORP sensors. The large display shows pH/ORP value simultaneously…

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EM805 – Smart modules (4-20mA or MODBUS/RS485) for S8000 Series

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