Dissolved oxygen analyzerThe core principle of evaluating water quality by detecting dissolved oxygen (DO) concentration in water is based on the reduction reaction or fluorescence quenching effect of oxygen molecules on the electrode surface, which can be mainly divided into the following two categories:

Electrochemical method (mainstream technology)

Polarographic electrode: A silver silver chloride electrode and potassium electrolyte are used. By applying a voltage of 0.5-0.8V, oxygen molecules diffusing to the electrode surface are reduced, generating a diffusion current proportional to the oxygen concentration.

Primary battery type electrode: silver and lead are used as electrodes, combined with potassium hydroxide electrolyte to form a half cell reaction, without the need for external voltage. The current generated by oxygen reduction directly reflects the concentration.

Advantages: Mature technology, low cost, suitable for continuous monitoring; Limitations: Electrolyte and film need to be replaced regularly, as they are susceptible to interference in high salinity or corrosive water bodies.

Fluorescence method (emerging technology)

Fluorescent substances (such as ruthenium complexes) have a shortened fluorescence lifetime with changes in dissolved oxygen concentration under specific wavelength light excitation. The oxygen concentration can be indirectly calculated by detecting the fluorescence decay time.

Advantages: No need to consume oxygen, fast response time (<10 seconds), simple maintenance (no need for electrolyte replacement); Limitations: High cost and high requirement for water quality transparency.