# Advice 1: How to find absolute humidity

Absolute humidity the mass of water vapour, which is located in unit volume of the gas, simply put, is the density of water vapor. Depending on temperature this value can vary. It can be measured, receiving the dew point or can be calculated via the relative humidity.
You will need
• - mercury thermometer;
• - sealed vessel;
• - the table is based on saturated steam temperature;
• - the psychrometer.
Instruction
1
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.
2
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.
3
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%).
4
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 measure humidity

Humidity measurement is necessary as physicists and weathermen. And ourselves this question, too, should be interested in, especially if we sit for a long time in the same room. Because humidity affects the human body because we need to control. There are two main types of instruments for measuring humidity. They differ in the device and principle of work. It hygrometers and psychrometers.
Instruction
1
The principle of operation of hygrometer is to analyze the effect of variations in humidity on a certain type of body and matter. For example, hair hygrometers based on the ability of skimmed human hair to change its length in response to changes in humidity. Such hygrometers measure the humidity in the range 30-100%. In film hygrometers moisture sensitive element is an organic film.
2
Although film and hair hygrometers are not able to give such accurate measurements, which is given by the psychrometer. But in winter, the main means of measuring the relative humidity of the air are all the same hygrometers, which are also the weight, the electrolytic condenser and ceramic. Each of these types of hygrometers has its own characteristics. But the base one for all: the hygrometric method of measurement or determination of the dew point.
3
Psychrometric method of measuring relative humidity is also very popular. The hygrometers accuracy can reach 5%, but psychrometers much more accurate. Standard the simplest psychrometer consists of two thermometers. One dry and the second wet. The second is wrapped in water soaked cotton cloth. Evaporating water cools the thermometer, and at this time the second (dry) thermometer shows the temperature of the surrounding air. Testimony in the end are transmitted to the evaluation unit, which determines the relative humidity of the indoor air based on the difference in temperature between the dry and wet thermometers.
4
If neither psychrometer or hygrometer you do not, humidity can be measured without them. Type in a glass of cold tap water and place it in the fridge for a couple of hours. Make sure that the water temperature has not dropped below \$ 5. Put a stack in the room so she was away from heaters. Now watch the pile for several minutes.
5
If the walls of the stack began to fog up and they're dry in five minutes, so the humidity is very low, that is, the air is dry;
On average humidity is "misleading" wall of the stack, and the remaining fogged;
If the surface of the glass within five minutes of the formation of small streams of water, so the humidity in the room high.
Note
If you have a special device to measure humidity – hygrometer, to determine what the humidity in the room is not difficult. But what if there is no such apparatus. Find the approximate values of the humidity in the apartment and on their own. How to measure humidity without a hygrometer. There is a fairly simple way.
In winter the air dries due to the Central heating, in summer it often happens that the humidity is very high. How to measure humidity in the apartment and bring it to normal? Depends on the humidity level of the concentration of moisture outside. In winter, this difference is significant as a result of the heating. To measure the humidity, use the good old hygrometer (personally I still have from my grandparents – 3 in 1: thermometer, hygrometer and barometer).

# Advice 3: 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.
Instruction
1
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.
2
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.
3
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 4: What is the absolute and relative humidity

Humidity – a feature which expresses the amount of water vapor in the air. This is one of the most significant indicators describing the weather and climate. Generally, in the Earth's atmosphere humidity varies over a wide range depending on altitude and climatic zone.

## Absolute humidity

Absolute humidity is the density of water vapor in the air, in other words, the mass of water vapor, which is actually fit in one cubic meter of air. The indicator is measured in grams per cubic meter.

The air is able to reach a state of complete saturation, this is due to the fact that at a constant temperature, it is able to absorb only a certain quantity of steam. So the absolute humidity (when the air is fully saturated) is called moisture capacity.

## Relative humidity

The absorption depends on the temperature, and increase increases dramatically. If we calculate the ratio of the absolute humidity of air at a specific temperature to its capacity at the same temperature will produce a measure called relative humidity.

If we analyze the values of the relative humidity across the Land, it is highest in the Equatorial zone, in the polar latitudes, and within continents, the average latitude in the winter, and lowest in the subtropical and tropical deserts. As altitude increases humidity decreases rapidly.

## How to find relative humidity

To determine the value of the relative humidity of the air used a special device – a psychrometer. In fact it is a system of two thermometers. One of them put a gauze case, the tip is lowered into the water. The second thermometer is in normal mode and shows the current air temperature. First, the thermometer with case, shows a lower temperature (because the evaporation of moisture from the case consumed heat).

The temperature value, which shows the wet thermometer, is called the limit of cooling, and the difference between the dry and wet – psychrometric difference. The relative humidity is inversely proportional to the psychrometric difference: the lower the humidity, the more moisture the air can absorb.

To obtain a numerical measure of the relative humidity need the value of absolute humidity divided by maximum possible humidity. Usually the result is expressed in percent.

The humidity indicator is very important, because if too low or high humidity deteriorating human health, reduced working capacity, deteriorating perception and memory. In addition, under strictly defined borders humidity required to store food, building materials and many electronic components.
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