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>> Figure 1
Oxygen concentration in water-saturated air depends on the temperature.
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Partial pressure is not the same as percent by volumeThe dynamic oxygen sensor determines the concentration of oxygen directly in the gas mixture to be measured. It determines the absolute oxygen content, i.e. the oxygen partial pressure, and not the relative content (percent by volume). | |  | | | Atmospheric air is composed of the gases nitrogen, oxygen, carbon dioxide, argon and water vapor. Thus, the total pressure of the air is the sum of the partial pressures.
- Dalton‘s law of partial pressure:
P(total) = P(N2) + P(O2) + P(CO2) + P(Ar) + P(H2O)
| | | | | This means that the oxygen partial pressure changes depending on (1) the atmospheric air pressure P(ges) and (2) the humidity of the air P(H2O).
When the air pressure increases and the humidity remains constant, the oxygen partial pressure increases, the percent by volume oxygen remains constant, however! (The absolute content of oxygen rises, the relative content remains unchanged.)
However, when the air pressure is constant and the humidity changes, the oxygen partial pressure and percent by volume oxygen change!
By the way: The more humid the air is, the less oxygen does it contain. This becomes particularly noticeable at high temperatures.
Fig. 1 : Oxygen concentration in water-saturated air depends on the temperature.
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