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.
Advice 2 : How to find relative humidity
To determine the relative humidity of the air learn real pressure or density of vapor at a given temperature, divide the value of the pressure of saturated steam at a given temperature, which can be found in the table and multiply by 100%. The relative humidity of the air can be found depending on the difference in the readings of dry and wet thermometers or change the length of the hair depending on the humidity.
You will need
- two identical thermometer, a piece of gauze, the hair psychrometer psychrometric table table of the dew-point.
Determination of relative humidity through the point resistente the temperature of the air and using the table to determine the saturated vapor pressure at a given temperature. Then collect a sample of air and cool it, by constantly monitoring the temperature until the water vapor in it begins to condense, forming dew. Measure the temperature at this point and using the table to determine the saturated vapor pressure. It will be equal to the actual vapour pressure at reference temperature. After that divide the vapor pressure obtained by cooling the saturated vapor pressure at a given temperature, and multiply the result by 100%. The result is relative humidity in percent.
The definition of relative humidity two will thermometrically two of the same thermometer. The best fit liquid mercury thermometers. On the bubble with the fluid of one of them wrap the cheesecloth, then wet it with water. After waiting some time, read thermometers in degrees Celsius. Then find the temperature difference between the wet and dry bulb thermometer readings wet bulb thermometer will be either the same or lower than the dry. In a psychrometric table, locate the column of the dry bulb temperature and look closest to what was demonstrated by the measurement. Then the line find the value that matches the calculated difference in the readings of dry and wet thermometers, the cell will be the relative humidity of the air in percent.
Determine the relative humidity the hair gidrometpostavka horse hair changes its length depending on the humidity of the air, pull it and attach to a sensitive dynamometer. The tension force can determine the relative humidity of the air. This measurement is the least accurate.
When calculating the saturated vapor pressure can be replaced by its density, the result is not affected.
Advice 3 : How to determine relative humidity
The discomfort causes too dry air, but the same feeling and will cause too high humidity air. To control and maintain the required limits of relative humidity of air should be able to define it. There are several types of special devices (glucometers), with which it is possible to measure the relative humidity of air: hairline, membrane, psychometric, weight (absolute).
You will need
- a small glass bowl, hairline, membrane hygrometers, 2 alcohol thermometer, a rectangular plate for thermometers, 6 clamps for mounting thermometers and tank water to a plate cylinder of water, a fabric wick.
There is a fairly simple way to find the approximate humidity of the air. Type water into a container and chill in the refrigerator until the temperature 2-3 degrees. Take it to the room and set away from heating appliances. View on the vessel wall after 5 minutes. Walls are dry – the humidity of air is low, a damp wall – humidity of the air medium, on the walls of the vessel appeared streams of water – the humidity of air is high.
Hairline hygrometer consists of a metal frame, a dial pointer and stretched between the pointer and carcass fat-free hair. This device uses the ability of the hair to change its length depending on the humidity of the ambient air. To measure put the hair hygrometer in the room. After 10 minutes read the readings.
In a membrane hygrometer humidity air takes the membrane from the organic matter. Change the position of the membrane when the relative humidity of the air are transmitted to attached to the arrow system. When measuring the humidity of the air in such a hygrometer wait 20 minutes, then read the readings.
More accurate readings of the psychrometer. In the absence of the factory is possible to make a homemade psychrometer. 4 attach the clamps 2 alcohol thermometer to the plate. Between 2 clamps attach the tank to the water. The container with alcohol one thermometer wrap the cloth and secure with string. The free edge of the fabric down into the tank with water. The humidity of the air , calculate according to the table, fixed on the image to step.