Glass ORP (Redox) Electrode – Key Features and Applications

A glass ORP (Oxidation–Reduction Potential) electrode measures the electrical potential generated by oxidizing and reducing substances in water, expressed in millivolts (mV). This value represents the real disinfecting power of the water, not just the chemical concentration.

How it works

The probe is made of three main elements:

• Platinum measuring electrode
  In direct contact with the water, it exchanges electrons with oxidizing agents (chlorine, chlorine dioxide, ozone, etc.) and generates a voltage proportional to the redox potential.

• Reference electrode in KCl electrolyte
  Provides a stable electrical reference.

• Ceramic junction (salt bridge)
  Allows ionic contact between the internal electrolyte and the process water, ensuring signal stability.

The difference in voltage between the platinum electrode and the reference electrode is the ORP value.

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What ORP indicates

ORP shows how strongly the water can destroy bacteria and organic matter:

• > 650 mV → effective disinfection

• 750–850 mV → strong oxidizing power

• < 500 mV → insufficient disinfection

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Main applications

Glass ORP probes are widely used in:

• Swimming pools and spas – control of chlorine, bromine, or salt electrolysis

• Drinking water treatment – monitoring disinfection efficiency

• Cooling towers – Legionella and oxidant control

• Industrial water and CIP systems

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Why use ORP instead of only chlorine

ORP measures the real disinfecting capability of water, taking into account:

• pH

• temperature

• organic load

• all oxidizing agents present

This makes it ideal for automatic dosing systems with pumps and controllers.

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