Relative Humidity Formula Using Dry Bulb And Wet Bulb Reading

The dry bulb wet bulb and dew point temperatures are important to determine the state of humid air.

Relative humidity formula using dry bulb and wet bulb reading. The relative humidity of the air is the ratio of the actual amount of moisture in the air to the fully saturated amount. 1 choose a temperature scale. Dry bulb temperature and. Consult a relative humidity chart or table.

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. Calculate temperature dewpoint or relative humidity tweet. Note that continuously air flow around the thermometer is important to evaporate. We can use evaporation to measure the amount of moisture in the air.

Just find where the dry bulb temperature and the difference between the wet and dry bulb readings intersect on the chart. Dry bulb temperature t db can be measured with a simple thermometer as shown above. Simple formula for computing relative humidity form readings of the dry and wet bulb thermometers. Search for more papers by this author.

Enter a temperature wet bulb and actual station pressure. When the psychrometer is swung around by its attached chain or handle the air causes the water on the wick to evaporate which. Fahrenheit celsius temperature t dewpoint t d. Use the link below to share a full text version of this article with your friends and colleagues.

Air humidity can be estimated by measuring. 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. 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.

3 press calculate to find the missing value. A wet cloth is placed over the bulb of a thermometer and then air is blown over the cloth causing the water to evaporate. By definition wet bulb temperature is the lowest temperature a portion of air can acquire by evaporative cooling only. 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.

2 enter values in 2 of the 3 boxes. Wet bulb temperature t wb can be measured with a standard thermometer with some wet clothing cotton or similar around the bulb. From these readings you can figure out the relative humidity.