The impact of mirror contamination on dew point meter measurements

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The impact of mirror contamination on dew point meter measurements In dew point measurement, mirror contamination is a significant issue, and its effects are manifested in two main ways: one is the Raoult effect, and the other is the alteration of the background radiation level of the mirror. The Raoult effect is caused by water-soluble substances. If the gas under test contains such substances (usually soluble salts), dew formation on the mirror occurs prematurely, resulting in a positive deviation in the measurement results. If the pollutants are water-insoluble particles such as dust, they will increase the background scattering level, thereby causing a zero drift in the photodiode dew point meter. Furthermore, the vapors of some substances with a boiling point lower than that of water (such as organic compounds) that are prone to condensation will, needless to say, interfere with the measurement of the dew point. Therefore, any type of dew point meter should prevent contamination of the mirror surface. Generally speaking, the impact of pollution from industrial process gas analysis is quite severe. But even in the measurement of pure gases, mirror contamination accumulates over time.