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.
Why is ORP Measurement Needed?
ORP measurements are a cost effective method used to monitor a variety of processes. Common applications include disinfection using chlorine, ozone, and bromine. All of these species are strong oxidizers, so ORP is used as an indicator of sanitizing activity. ORP is also used in process applications to monitor destruction of chromate or cyanide, as well as in bleach production and wet scrubbers.
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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.
Popular ProductsSensorex ORP Best Sellers
TX100 pH/ORP Loop Powered 4-20mA Transmitter
Our TX100 is a fully-featured ORP/pH transmitter for use with pH and ORP sensors. The large display shows pH/ORP value simultaneously with…
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…
S8100 – Process ORP Sensor, Submersion
Our S8000 series ORP sensors deliver the most reliable online ORP monitoring in a unique, modular package that minimizes total…
EM805 – Smart modules (4-20mA or MODBUS/RS485) for S8000 Series
The EM805 is our most cost-effective solution for connecting our S8000 series pH and ORP sensors to a PLC or…
S8200-ORP – Modular In-line ORP Sensors
The S8200-ORP is a self-cleaning ORP sensor that delivers the most reliable online monitoring in a unique, modular package that…
ORP1000 – ORP Sensor, Polycarbonate Laboratory
The ORP1000 is a durable and easy to use ORP sensor. Great for outdoor applications, such as monitoring swimming pool…
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…
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…
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In addition to ORP sensors we have a full range of water quality sensors.
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