Analysis of the role of dissolved oxygen sensor

1. Optimizing the biodegradation process in wastewater treatment plants by measuring and adjusting oxygen levels in activated sludge tanks.

2. Monitoring water quality in rivers, lakes, and oceans by assessing oxygen content, which is an essential indicator of ecological health.

3. Supporting water treatment processes such as oxygen enrichment or corrosion prevention in drinking water systems.

4. Maintaining healthy aquatic environments in fish farms by regulating dissolved oxygen levels for optimal fish growth and survival.

The solubility of oxygen in water is influenced by factors such as temperature, pressure, and the presence of dissolved salts. A typical dissolved oxygen sensor consists of a gold electrode (cathode) and a silver electrode (anode), along with an electrolyte solution like potassium chloride or potassium hydroxide. Oxygen molecules diffuse through a permeable membrane into the electrolyte, forming an electrochemical cell with the two electrodes. When a polarization voltage of 0.6 to 0.8 volts is applied, oxygen reacts at the cathode, releasing electrons, while the anode accepts them, generating an electric current. The chemical reactions involved are:

Anode: Ag + Cl⁻ → AgCl + 2e⁻

Cathode: O₂ + 2H₂O + 4e⁻ → 4OH⁻

According to Faraday’s laws of electrolysis, the current produced is directly proportional to the partial pressure of oxygen. At a constant temperature, this current also has a linear relationship with the actual dissolved oxygen concentration.

Currently, high-quality dissolved oxygen sensors are still dominated by international brands. One of the most reliable options is the KDS-25B, developed by Japan's FIGARO company. This shallow dissolved oxygen sensor is a galvanic-type device specifically designed for water quality control. It stands out due to its long service life and resistance to interference from COâ‚‚, making it ideal for long-term monitoring applications.

The KDS-25B uses a unique acidic electrolyte, with a gold cathode and a lead anode. Oxygen diffuses through a fluororesin membrane, participating in redox reactions that generate a small current. This current is then converted into a voltage output using internal resistance. The magnitude of the current is directly proportional to the dissolved oxygen concentration—essentially, the more oxygen present, the greater the number of oxygen molecules passing through the membrane and contributing to the reaction.

With its accuracy, stability, and durability, the KDS-25B is widely used in environmental monitoring and water quality testing. Whether for industrial applications or ecological research, it offers a reliable and efficient solution for real-time dissolved oxygen measurement.