Dissolved oxygen analyzers work based on the technology of METTLER TOLEDO in-line DO sensor selected. METTLER TOLEDO offers two in-line DO sensor technologies: Amperometric and Optical.
Amperometric: These in-line dissolved oxygen sensors use a gas permeable membrane to separate the sample from the electrochemical cell inside. Oxygen diffuses through the membrane in direct proportion to the partial pressure of oxygen in the liquid outside the in-line DO sensor. A cathode and anode inside the probe are polarized with a voltage to enable the electrochemical reaction of oxygen. Oxygen is reduced at the cathode while the anode is oxidized, producing a small current in direct proportion to the amount of oxygen in the sample. In addition, the dissolved oxygen sensor uses the temperature value to convert the oxygen partial pressure signal to a dissolved oxygen concentration value by compensating for the changing solubility of oxygen with temperature.
Optical: These in-line dissolved oxygen probes use optical technology for measurement. They contain an oxygen-sensitive layer that can fluoresce. This layer absorbs light from a light emitting diode in the sensor, and the light is released as fluorescence. The fluorescence lifetime depends on the amount of oxygen present in the sample medium.