ORP Calibration Basics

ORP Sensor Design

Oxidation-reduction potential, or redox potential, is a measure of the chemical exchange of electrons between multiple species in a solution. ORP sensors use an electrochemical measurement principle similar to pH and contain both a measurement and a reference half-cell electrode. In place of a pH-sensitive glass membrane, typical ORP probes use a measurement electrode, usually made of a noble metal such as platinum.

To offset the electric potential of the sensor derived from individual components of the reference and measuring electrodes, a calibration is performed. In ORP, this is done by standardizing a sensor against a solution of known oxidation-reduction potential.

ORP Calibration and Temperature

A single-point calibration is performed using an ORP liquid buffer of a known value. Temperature is an important consideration when calibrating and measuring ORP, as temperature can influence the availability of free protons. Hamilton ORP buffers come with a standard table of ORP values at various temperatures. If an Arc ORP sensor is used, the ORP buffer value is automatically recognized within ArcAir software. Any temperature-related correction is compensated for by the built-in RTD. For non-Arc ORP sensors, temperature should be manually compensated at the transmitter.

Hamilton Redox (ORP) Buffer 475 ± 5 mV (Ref 238227)

Celsius	mV*	mV**	Celsius	mV*	mV**	Celsius	mV*	mV**
5	456	677	20	470	681	35	484	684
10	461	678	22	472	681	40	488	684
15	465	679	25	475	682	45	492	684
18	468	680	30	479	683	50	496	684

* E(Reference Potential based on Ag/AgCl element with 3M KCl electrolyte found in Hamilton sensors)

** E(Pt, Hydrogen)

ORP Sensor Design

ORP Calibration and Temperature

Hamilton Redox (ORP) Buffer 475 ± 5 mV (Ref 238227)

Hamilton Duracal ORP Buffers come in 271 and 475 mV standards

Related Content

Celsius	mV*	mV**	Celsius	mV*	mV**	Celsius	mV*	mV**
5	456	677	20	470	681	35	484	684
10	461	678	22	472	681	40	488	684
15	465	679	25	475	682	45	492	684
18	468	680	30	479	683	50	496	684

Celsius	mV*	mV**	Celsius	mV*	mV**	Celsius	mV*	mV**
5	456	677	20	470	681	35	484	684
10	461	678	22	472	681	40	488	684
15	465	679	25	475	682	45	492	684
18	468	680	30	479	683	50	496	684

Celsius	mV*	mV**	Celsius	mV*	mV**	Celsius	mV*	mV**
5	456	677	20	470	681	35	484	684
10	461	678	22	472	681	40	488	684
15	465	679	25	475	682	45	492	684
18	468	680	30	479	683	50	496	684