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Relative Humidity can be measured with a psychrometer. A psychrometer has two thermometers, a wet-bulb and dry-bulb. The wet-bulb has a wet cloth on one end. If the wet-bulb is colder than the dry-bulb, than you apply the information to a psychrometer chart, which tells you the relative humidity, from which you can determine "high" or "low". http://andrewslog.files.wordpress.com/2008/04/48d16354-752c-4965-9c43-024073c31186.jpg
2 instruments are required to accomplish these measurements:a barometer to measure atmospheric pressure.a hygrometer to measure humidity.
You measure humidity with a psychrometer. It is a tool that has 2 thermometers connected to either side of a piece of material. One of the thermometers is normal and the other one has a wet sock on it. To use the psychrometer you spin it for 2 minutes or so and you take the temperature on the dry bulb thermometer (the normal one) and take the temperature of the wet bulb thermometer (the one with the wet sock on it). The wet one will dry out more if there is less moisture in the air because as you are spinning it you are evaporating the water into the air. The dryer air can hold more water than moist or humid air. By comparing the two numbers you can figure out the wet bulb depression, the dewpoint, and the relative humidity.
1) Warm air can hold/contain more water vapor than cool air. 2) Relative humidity is a measure of how much water is in the air as compared to the maximum it can hold. Thus if you take some warm summer air and send it into a nice cool basement, the air will cool and as cool air can hold less water than the warm air, the relative humidity of the cooled air in the basement will go up.
Answeractuall humidity is given as the amount of water. use a table stating how much water the air can hold at the given temp, this is your 100% humidity. now calculate howw much you got and that would be relative humidityAnswer:To calculate relative humidity you need a wet bulb and a dry bulb thermometer and a psychrometric chart (a graph of the physical properties of moist air at a constant pressure). The chart graphically expresses how various properties relate to each other.Using an ordinary thermometer you read the dry bulb temperature(DBT). You will locate this temperature on the x-axis of the chart.Next you will determine the wet bulb temperature (WBT) from a thermometer who's bulb is covered with a wet wad of cotton and typically waved in the air until the temperature goes to its minimum. This works because dry air evaporates water and evaporation cools the wad. The temperature it reaches is related to the air's humidity. This value goes on the curved line at the top of the chart.The relative humidity (RH) is read off the chart from the intersection of the lines from these two points.
Relative Humidity can be measured with a psychrometer. A psychrometer has two thermometers, a wet-bulb and dry-bulb. The wet-bulb has a wet cloth on one end. If the wet-bulb is colder than the dry-bulb, than you apply the information to a psychrometer chart, which tells you the relative humidity, from which you can determine "high" or "low". http://andrewslog.files.wordpress.com/2008/04/48d16354-752c-4965-9c43-024073c31186.jpg
A sling psychrometer (or hygrometer) uses the difference in readings between a wet bulb thermometer and another with a dry bulb to measure the relative humidity. The bulb that is wet will cool by evaporation to the "dew point", which is the temperature at which the current humidity would be the maximum possible. Comparing that to the dry bulb (the general air temperature) on a comparative chart will yield the approximate relative humidity.
1. About Digital Thermometers 2. Appliance Thermometers 3. Bimetallic-Coil Thermometers 4. Calibrating the Thermometers 5. Cooking Temperatures
Relative humidity means the percentage of water vapor in the air compared to the total amount that could be contained. Or the measure of the amount of water vapor that air is holding compared to the amount it can hold at a specific temperature. This is different at different temperatures. Here are a couple of sentences:1. The relative humidity is 10 percent.2. We studied relative humidity in class.3. Saturation air has a relative humidity of 100 percent.
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2 instruments are required to accomplish these measurements:a barometer to measure atmospheric pressure.a hygrometer to measure humidity.
A sling psychrometer an instrument that measures relative humidity (a hygrometer). The sling has two thermometers, a dry bulb and a wet bulb thermometer, mounted together on a chain. The wet bulb thermometer is wrapped in muslin that is moistened with distilled water. The user then swings the sling until the temperatures stabilize, then quickly notes the two temperatures. To interpret the readings and determine the humidity, a chart is then used for the specific altitude at which the reading was taken. Basically, the drier the air is, the more moisture evaporates from the moistened muslin-covered thermometer, and the greater the difference between the two thermometers. If the relative humidity is 100%, then the two temperatures will be the same. Slings have been around for years, and are becoming less and less used for many reasons. With the advent of digital hygrometers, it's just easier to pull out a device and read the screen. Additionally, besides being cumbersome and time consuming, slings contain mercury, a hazardous material, and must be handled with care. A sling will typically read 5-10% high due to user error. Some of the mistakes that can be made while using a sling are: 1. If the sock on the wet bulb thermometer is not clean, the humidity measured from a sling will err on the high side. 2. If the water used for the wet bulb thermometer is not distilled water, the humidity measured from a sling will err on the high side. 3. If the sling is not swung around long enough, the humidity measured from a sling will err on the high side. 4. If the thermometer measurements are not read quickly enough after swinging the sling, the humidity measured from a sling will err on the high side. 5. If the charts used to interpret the results are not for the same altitude where the readings were taken, the humidity will be incorrect. Additionally, the charts are only available in 100' increments, and it is often difficult to determine the exact altitude of the user.
Water vapor in the air is absolute humidity. The ratio of the absolute humidity to the maximum absolute humidity for that temperature and pressure is called the "relative humidity." Absolute humidity is very frequently expressed in terms of grains per pound of air, ppm, or vapour pressure. Relative humidity is usually expressed as a percent.Relative humidity, expressed as a percentage from 0% to 100%, is the amount of moisture in air divided by the total possible amount of moisture in air. Unfortunately, the total possible amount changes when the temperature changes, so the relative humidity can change without adding or removing any water.Another measure is dew point, which is the temperature at which water would condense. It doesn't change with temperature.The lowest measured relative humidity in Phoenix, AZ, USA, is 2%--pretty dry. Sometimes the dew point is below 0 degrees, also pretty dry. (Celsius or Fahrenheit? Both!)
I think it's 20% because 2/10 is 1/5 or 20% of the total water it can hold.
Different types of humidity (specific, relative, and vapor pressure) are all measured with different units, although weathermen usually express the relative, which is measured as a percentage. For further help, I've attached a link in the related links below.
One can calculate the absolute humidity (AH) from the relative humidity (r) using three equations: (1) the equation for mixing ratio, (2) an equation for relative humidity expressed in terms of mixing ratio, and (3) the Clausius-Clapeyron equation, which relates saturation vapor pressure to temperature. The result of combining the three equations is: AH = (1324 r/T) [exp {5417.75 (1/273 - 1/T)}] where AH is expressed in grams per cubic meter, T is temperature in Kelvin, r is relative humidity (range is 0 to 1), and the relation holds true for T>273. For T<273, replace 5417.75 with 6139.81.
That is very dry air or about 20% humidity