The optical sensor method measures dissolved oxygen concentration by utilizing the change in fluorescence emission time caused by the sample's concentration after irradiating a fluorescent film in contact with the sample with excitation light.
An oxygen detection membrane is placed on the side touching the sample in a transparent window. This oxygen detection membrane contains fluorescent substances, and when it is irradiated for a certain time with excitation light, fluorescence and phosphorescence occur. When the oxygen detection membrane is not in contact with oxygen, the time light is emitted is longer, and when it is in contact with oxygen, the oxygen molecules absorb the excitation energy, so the time light is emitted is shorter. Measuring the time light is emitted makes it possible to detect the dissolved oxygen concentration in the sample.
In this measurement process, oxygen in contact with the oxygen detection membrane is not consumed, so there is no impact on the dissolved oxygen concentration near the oxygen detection membrane. Measurements are possible therefore even with samples for which flow velocity cannot be determined.
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