Relative Humidity Formula Using Dry Bulb And Wet Bulb Reading

Simple formula for computing relative humidity form readings of the dry and wet bulb thermometers.

Relative humidity formula using dry bulb and wet bulb reading.

We can use evaporation to measure the amount of moisture in the air. Consult a relative humidity chart or table. Wet bulb temperature t wb can be measured with a standard thermometer with some wet clothing cotton or similar around the bulb. Relative humidity is measured using a device called a sling psychrometer this consists of 2 side by side conventional thermometers one of which the wet bulb thermometer has a wetted wick placed at the bottom the other the dry bulb thermometer has no wetted wick.

Relative humidity is determined from the wet and dry bulb temperature readings using a table or slide calculator. 3 press calculate to find the missing value. Dry bulb temperature t db can be measured with a simple thermometer as shown above. Calculate temperature dewpoint or relative humidity tweet.

2 enter values in 2 of the 3 boxes. The relative humidity of the air is the ratio of the actual amount of moisture in the air to the fully saturated amount. In of mercury mm of mercury millibars hpa. The knowledge of only two of these values is enough to determine the state of the moist air including the content of water vapor and the sensible and latent energy enthalpy in the air.

1 choose a temperature scale. By definition wet bulb temperature is the lowest temperature a portion of air can acquire by evaporative cooling only. Note that continuously air flow around the thermometer is important to evaporate. Enter a temperature wet bulb and actual station pressure.

From these readings you can figure out the relative humidity. A wet cloth is placed over the bulb of a thermometer and then air is blown over the cloth causing the water to evaporate. Then they sling the thermometers around for 3 minutes and read the wet bulb temperature. Search for more papers by this author.

Enter your actual station pressure not the altimeter setting. It includes a dry bulb thermometer a wet bulb thermometer and a psychrometric chart a graph that plots the relationships between the dry and wet bulb temperature relative humidity and dew point at constant pressure. Dry bulb temperature and. The dry bulb wet bulb and dew point temperatures are important to determine the state of humid air.

When the psychrometer is swung around by its attached chain or handle the air causes the water on the wick to evaporate which. Just find where the dry bulb temperature and the difference between the wet and dry bulb readings intersect on the chart. The sling psychrometer has water in it to wet the bulb of one of the thermometers and read the temperature of the dry bulb thermometer.