How an Optical Oxygen Sensor works
How is it possible that the oxygen concentration in beverages can be quantified by means of light?
Few components provide a lot of information
An optical oxygen (O2) sensor quickly and reliably detects the amount of O2 in liquid or gaseous media. Generally, the O2 measurement remains unaffected by other gases. An optical O2 sensor consists of
- a light-emitting diode (LED),
- an inert carrier holding the light-sensitive layer where dye molecules are embedded in a polymer matrix and protected by an optical insulation layer,
- and a photodiode plus filter to quantify the emitted light.
What happens in the absence or presence of oxygen?
If no O2 is present in the sample, the dye absorbs excitation light, emitted by the LED, gets transferred to a higher energy level and emits light again. The emission light is time-delayed and has a different wave length. The filter in front of the photodiode ensures that only emitted light is detected.
Is O2 present in the sample, the dye absorbs excitation light, but in its excited state the energy is taken over by O2 molecules. The dye has now less energy left to emit. The more O2, the less emitted light gets to the photodiode.
The sensor’s characteristics speak for themselves:
- Non-destructive: no oxygen consumed during measurement
- User-friendly: no electrolyte needed, no polarization time required
- Ecologically friendly: no chemicals required
How to quantify the O2 concentration ?
The emission light is time-delayed with respect to the excitation light. The time shift between excitation and emission light is independent from the intensity. It is proportional to the partial pressure of O2 and acts as a measure for the O2 concentration.
Good to know
Did you know that different polymer matrices and different dyes influence the properties of the sensor, for example its sensitivity in certain ranges?