You will need
- - mercury thermometer;
- - sealed vessel;
- - the table is based on saturated steam temperature;
- - the psychrometer.
For direct humidity measurement, collect a sample of air in a sealed vessel and begin to cool it. At a certain temperature in the vessel will appear Rosa (par condenseries), record the temperature value at which it will happen. Specially the table, find the density of saturated steam at the temperature that it was condensed. This will be the absolute humidity of air, the sample which was selected.
Take a sensitive mercury thermometer, wrap the vial with mercury cloth. Clear with his statement after he will come to thermal equilibrium with the surrounding air. On the table to determine the density of saturated vapor at the temperature recorded by the thermometer. This will be the absolute humidity, but the value is not very accurate.
Calculate absolute humidity at a known relative humidity. This value is measured in percentage and indicates how many times the actual density of water vapor in the air is less saturated at a given temperature. To determine the absolute humidity measure the temperature of the air. Then, the density table of saturated steam, find the value for the measured temperature. To find the absolute humidity, the relative humidity φ and multiply by the density of saturated steam at a given temperature, pH and divide by 100% (ρ= φ∙ pH/100%).
An example of relative humidity at 20 ° C. is 45%. To obtain the absolute humidity, find the density of saturated steam at a temperature of 20 ° C, which has air. This value is 17.3 g/m3. Then, apply the formula to calculate absolute humidity ρ=45∙to 17.3/100=7,785 g/m3. This will be the absolute humidity of the air.
If the relative humidity is unknown, measure it with a special instrument called a psychrometer.