In daily life, we can see that when the temperature of the air decreases at night, a portion of the water in the air will precipitate, forming dew or frost. This indicates that under the condition of constant water vapor content, due to the decrease in temperature, the previously unsaturated water vapor in the air can become saturated vapor, and excess water will precipitate. The temperature at which water vapor reaches saturation is called the "dew point".
By measuring the dew point temperature, the water vapor content can be obtained from the saturation content of the water vapor. Due to the fact that the water vapor content does not change during the temperature reduction process, measuring the dew point actually measures the absolute humidity in the air. If the dew point is lower, it indicates that the moisture content in the air is less.
The dew point can be measured using a dedicated dew point meter. For example, the dew point of air after passing through a dryer is -50 ℃, and the corresponding saturated moisture content at -50 ℃ is 0.038g/m3, indicating that the air still contains this moisture. If the dew point is -60 ℃, the saturated moisture content is 0.011g/m3. The lower the dew point, the higher the degree of dryness.
