ORP Meters: What, How, and When Answered

Posted by David Cannon on 20th Aug 2020

ORP Meters: What, How, and When Answered

ORP is quite a popular term in water quality measurement. ORP is an acronym for Oxygen Reduction Potential. It is also recognized as the redox potential of water. What exactly does ORP mean? It is a measure of how oxidizing or aerated the water is. Higher the ORP, the higher is the oxygen level in the water. This means ORP is basically merit of cleanliness and healthiness of the water. Owing to this ORP is such an important term in water quality measurement. The ORP meters are utilized to measure the quality of water. Some common applications of these ORP meters are water disinfection units, industrial water processing plants, drinking water supply centers, etc. If you intend to know more about ORP meters, what they are, how do they work and when to use them, then this post is for you. This post discusses answers to all these questions.

What Are ORP Meters?

The  ORP meters are the devices designed for the measurement of the oxidation-reduction potential of water. ORP meters are also industrially known as a redox probe. These chemical or microbial species form redox couple, which results in electron loss. The ORP meters measure the number of electrons lost as a merit of the redox potential of the water.

When To Use ORP Meters?

The ORP meters are used when the water quality in terms of sanitization or contamination is to be measured. The ORP meter measures redox potential by measuring the electromotive force of the electron taken to pass it from reduced species to the oxidized species. These ORP meters cannot be used for all types of water testing. The factors like pH level have a high impact on the ORP readings. If the pH of water is higher than 9.5, then ORP meters become an invalid method of water quality measurement.

Therefore, the answer to when to use ORP meters becomes a little complex. Although, a simplified answer to this question can be to use when the water is being treated or processed. The following are a few examples of applications where ORP meters can be used to identify water quality.

  • Chlorinated swimming pools water testing
  • Oxidized or sanitized water storages
  • Drinking water distribution units
  • Wastewater treatment plants

Now that it discussed where and when one can use the ORP meters, then let us take forward to how ORP Meter works.

How ORP Meter Works?

The working principle of an ORP meter or redox meter is quite simple. It is a measurement of water’s capacity for electron transfer. The ORP meter consists of an electrode that is used as a probe or sensor to measure the redox potential of water. The working is similar to pH measurement. Just like the pH of a solution is measured based on hydrogen ion activity, the ORP measurement is a result of electrons’ movement inside the water. Depending on the quality of water, the ORP electrode acts as an electron donor or acceptor. If the contaminants in water are reductant, then the ORP electrode acts as an acceptor. If the contaminants are being oxidized then the ORP electrode acts as a donor. During this electron transfer, the potential difference is generated owing to the electromotive force. This potential difference is measured by the Aqua-logger or Aqua-meter to give a reading according to the ORP scale. Therefore, ORP meters are also known as differential ORP probes.

The ORP electrodes are designed to 0mV reading that is null reading at 7pH. As the pH value deflects over or below 7, the deflection in ORP is seen. The extreme range of ORP meter reading remains between -1500mV to1500mV.

Now that the introduction, working, and applications of ORP probes are discussed, it is essential to know that the quality of the ORP meter also impacts the results. Therefore, one must buy from trusted suppliers like Cannon Water Technology, Inc. being water technology specialists, the company offers a wide range of ORP Meters from several brands like Sensorex, HM Digital, Myron L etc.

HM Digital ORP-200 Waterproof ORP Meter

Myron L Ultrapen PT3 Pocket Tester Pen For ORP Testing

SP-700/B pH/ORP Sensor Module

Myronl L UltrapenX2 PTBT3 ORP (REDOX) and Temperature, Bluetooth Enabled

Myron L Ultrameter 6PIIFCE Hand-held Device


Myron L PoolPro PS6FCE Ultrameter Series II