ORP Sensors & Transmitters

ORP Sensors & Transmitters

Oxidation-reduction potential (ORP) measurement indicates the electron activity of a solution, reflecting its tendency to oxidize or reduce. ORP sensors use a noble metal measuring electrode and a reference system to produce a millivolt signal that changes with redox conditions. A transmitter conditions the signal, provides temperature input if required, and outputs a stable value for monitoring, alarming, or control.

The value of ORP is its ability to summarize complex chemistry into a practical control variable. In many processes, a single ORP setpoint can maintain the desired oxidizing or reducing environment, making it useful where direct measurement of every species is impractical. ORP responds quickly to chemical addition and process shifts, supporting stable control of disinfection, dechlorination, cyanide destruction, and other redox-driven reactions.

Typical applications include wastewater treatment (anoxic zone control, denitrification monitoring, and optimization of chemical dosing), drinking water treatment (oxidant demand tracking and dechlorination), and industrial oxidation processes such as sulfide control and odor mitigation. ORP is also used in metal finishing, mining, and chemical manufacturing to monitor reduction/oxidation stages, ensuring consistent reaction endpoints and minimizing reagent overuse.

Sensor performance depends on reference stability, cleanliness, and proper installation. ORP is sensitive to coatings, scaling, and biofilm, which can slow response and shift readings. Stable flow conditions and avoidance of air entrainment improve measurement consistency. Because ORP is an indirect parameter, commissioning should include correlating ORP values with process outcomes and defining meaningful alarm limits based on real operating data.

Operationally, transmitters with diagnostics help identify electrode poisoning, reference depletion, and abnormal impedance before readings become misleading. Routine cleaning, verification, and periodic sensor replacement maintain response speed and confidence. When paired with pH, dissolved oxygen, or chlorine signals, ORP becomes even more informative for diagnosing process health and controlling complex water chemistry.

Forberg Smith, an exclusive authorized representative of sales and service for Endress+Hauser.