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Dissolved Oxygen Sensors

Dissolved Oxygen

Dissolved oxygen refers to the level of free, non-compound oxygen present in water or other liquids. Non-compound oxygen, or free oxygen (O2), is oxygen that is not bonded to any other element. Dissolved oxygen is the presence of these free O2 molecules within water. The bonded oxygen molecule in water (H2O) is in a compound and does not count toward dissolved oxygen levels.

Dissolved Oxygen Sensors

AquaSensor offers two types of dissolved oxygen sensors, galvanic and optical. Galvanic sensors are electrochemical with electrodes of dissimilar metals. Metals have different electro potentials based on their activity series (how readily they give or accept electrons). When placed in an electrolyte solution, the potential between dissimilar metals causes them to self-polarize. The anode in a galvanic dissolved oxygen sensor is usually zinc, lead or another active metal while the cathode is silver or another noble metal. The dissimilar electrodes self-polarize, with the electrons traveling internally from the anode to the cathode. The cathode remains inert, serving only to pass on electrons and it does not interfere in the reaction. Thus the anode is oxidized and oxygen is reduced at the surface of the cathode.

Optical dissolved oxygen sensors measure the interaction between oxygen and certain luminescent dyes. When exposed to blue light, these dyes become excited (electrons gaining energy) and emit light as the electrons return to their normal energy state. When dissolved oxygen is present, the returned wave lengths are limited or altered due to oxygen molecules interacting with the dye. The measured effect is inversely proportional to the partial pressure of oxygen. Optical dissolved oxygen sensors can measure either the intensity or the lifetime of the luminescence, as oxygen affects both.


  • Potable Water
  • Industrial Water
  • Municipal Waste Water
  • Agriculture
  • Food & Beverage
  • Wineries
  • Fish Farming
  • Aquariums