What Are the Functions of ORP Sensor

Written by: kiancrogers

The Oxidation-Reduction Potential measures the tendency or capacity of a chemical system to donate or accept electrons in a redox reaction. The measuring ORP is called an ORP sensor and can be used for research and industrial applications. In this article, we will discuss the functions of the ORP sensors and how they work.

Measure the Concentration of Hydrogen Ions in a Solution

This type of sensor is known as a pH sensor. As hydrogen ions increase in concentration, the hydronium (H3O+) ions disproportionally decrease, which can be determined by measuring the ORP. This is because hydroxide anions attract electrons more easily than hydrogen ions do. Hence, as hydroxide concentrations increase, fewer available electrons are used in the reaction. This means that the equilibrium of the water molecules will shift towards hydroxide and not hydrogen, leading to a decrease in hydrogen ion concentrations.

Measure Redox Reactions

Redox reactions involve a change of the oxidation state of an element or atom. Since these reactions involve a substance gaining or losing electrons, the ORP in a solution measures how readily a substance gains or loses these electrons. An electron-transferring reagent, such as chromium(VI) oxide (CrO), can be added to solutions containing other elements to determine redox potentials.

Measure Dissolved Oxygen Concentration

The ability of an ORP sensor to measure dissolved oxygen concentrations is based on the reactions involved in natural water purification. Organisms, such as algae and cyanobacteria, produce oxygen during photosynthesis, so naturally occurring bodies of water are usually very high in dissolved oxygen concentrations. However, this can be bad for fish because too much-dissolved oxygen can interfere with their respiratory systems. This can generally be resolved by adding certain chemicals, but the process is costly and time-consuming. A more efficient way of solving this problem is to measure the dissolved oxygen concentrations using an ORP sensor, which can be done very accurately.

Measure Oxidation-Reduction Reactions in Biological Systems

It is often essential to know whether a reaction is an oxidation-reduction reaction in biological systems. In many cases, the difference between these two kinds of responses can be determined using an ORP sensor. For example, hydrogen peroxide oxidizes glucose by transferring electrons from the hydroxide ions to organic molecules in the solution. As a result, oxygen is produced, and the ORP in the solution decreases. By using an ORP sensor to measure this reaction, we can determine whether it is a redox reaction or not.

Measure Dissolved Oxygen Concentrations in Water Samples

Since dissolved oxygen concentrations are essential in many water purification systems, testing for dissolved oxygen concentrations is necessary. This can be done using an ORP sensor, which measures redox reactions involving the transfer of electrons to or from molecules present in the solution (such as dissolved oxygen). This is especially useful when determining whether a water sample has been contaminated with organic compounds because many pollutants increase the degraded oxidation-reduction potential in the water. Using an ORP sensor, the concentration of dissolved oxygen can be determined to distinguish contaminated water samples from uncontaminated samples with organic contaminants.

Measure Nitrification in Water Samples

Nitrification is when ammonia (NH3) is oxidized into nitrate (NO3-) ions, with oxygen as an electron acceptor. This can be determined using an ORP sensor because the transfer of electrons to the acceptors occurs, leading to a decrease in potential. For this reason, an ORP sensor can be used to determine whether or not nitrification has taken place. This is important because if nitrification hasn’t occurred, the ammonia will accumulate in water samples until it reaches dangerous concentrations.

Measure Dissolved Oxygen Concentrations in Biological Samples

As mentioned above, dissolved oxygen concentrations are essential for determining whether biological samples contain contaminants. For this reason, an ORP sensor can be used to make accurate ORP measurements of dissolved oxygen concentrations in these kinds of samples.

Measure Toxicity

In some cases, it is necessary to determine whether a specific chemical or compound is toxic by using an ORP sensor. For example, when organic pollutants are detected in water samples, an ORP sensor can measure the dissolved oxygen concentrations and determine whether they have been affected by the contaminant in a way that causes a change in the redox potential of the solution. This will indicate whether or not the pollutant is toxic to fish and other living organisms that rely on dissolved oxygen for breathing, so knowing this information can help prevent further damage to water systems.

Measure the Hydrogen Peroxide Concentration in Your Saliva

After you use mouthwash, if you swish with a mouthwash containing hydrogen peroxide (like Listerine) for 30 seconds, the amount of oxygen given off is enough to change the potential of an ORP sensor that is placed in your mouth. A negative ORP reading indicates that hydrogen peroxide is present rather than oxygen. This can be used to determine whether or not there are harmful levels of hydrogen peroxide in your mouth after using a mouthwash that contains this chemical.


By knowing this information, we can accurately measure many different chemicals and compounds that affect our environment without destroying samples or waiting several days for results. For this reason, an ORP sensor can help make accurate measurements in a wide range of areas.