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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.

ORP

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

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Popular ProductsSensorex ORP Best Sellers

B225 Zobell ORP Calibration Solution

Use this pre-mixed ORP calibration solution for verifying and calibrating ORP sensors. The solution standard is 228mV and is widely…

Add to Cart | $25.41

S465C-ORP – ORP (REDOX) Sensor, Extended Life Acu-Trol Direct-Fit Replacement

Our S465 series of ORP sensors deliver reliable online ORP (REDOX) monitoring as a direct-fit replacement for the Acu-Trol ORP sensor…

Add to Cart | $185.47

EM802-EC – Smart Conductivity Modules (4-20mA or MODBUS/RS485) for S8000 Series

The EM802-EC is our most cost-effective solution for connecting our S8000 series Contacting Conductivity sensors to a PLC or SCADA…

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EM803 – Smart modules (4-20mA or MODBUS/RS485) for S8000 Series

The EM803 is our most cost-effective solution for connecting our S8000 series pH and ORP sensors to a PLC or…

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TX2000 – pH & ORP Transmitter/Controller, Intelligent

Our TX2000 is an intelligent pH and ORP transmitter/controller for reading pH and ORP sensors and programmable process controls. The large…

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S420C-ORP/BTD – ORP (REDOX) Sensor, Extended Life Strantrol Direct-Fit Replacement

Our S420 series of ORP sensors deliver reliable online ORP (REDOX) monitoring as a direct-fit replacement for Strantrol ORP sensors W2T3067…

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S8000CD-ORP – ORP Sensor Cartridge for S8000 Series Kits, Quick Change

Our S8000 series of ORP deliver the most reliable online ORP monitoring in a unique, modular package that minimizes total cost…

Add to Cart | $232.25

SD7420CD-ORP – Differential ORP Probe with Direct 4-20mA Output

When an ORP sensor is constantly measuring a wastewater treatment process, it will be exposed to chemicals, suspended solids, and…

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