Dissolved oxygen (DO) is a measure of the amount of dissolved oxygen in a system / medium. Measurements are often taken on water samples using a DO probe and meter. When conducting dissolved oxygen testing in the field or laboratory, it is important to consider what type of dissolved oxygen technology is right for you.
Electrochemical sensors include both galvanic and polarographic types. A thin, permeable membrane gas isolates the sensor elements from water. The oxygen that passes through the membrane is reduced, creating a current that the meter converts into a measurement of oxygen concentration. Although electrochemical sensors are initially less expensive, they require frequent maintenance and depend on a constant sample flow for an accurate reading (since they consume the oxygen that permeates through the membrane).
Optical sensors are the other type of common dissolved oxygen sensor measured under the principle of fluorescence quenching. A luminophore that is part of the membrane is excited with the light of a blue LED, emitting in turn a red light. Dissolved oxygen in the sample ‘turns off’ this excitation.