How Do You Measure Temperature & Humidity?
You can measure relative humidity with what is called a sling psychrometer. It consists of two thermometers, one of which has a piece of cloth on the bulb that you dampen. The other thermometer measures the actual temperature. Moisten the piece of cloth attached to the wet-bulb thermometer. This cloth covers the mercury-filled bulb. Swing the two thermometers with the handle. About five minutes is enough time to give water on the wet cloth time to evaporate. The wet-bulb thermometer reading will drop as higher-energy water molecules evaporate, leaving behind cooler molecules. Use the built-in scale to compare the dry- and wet-bulb temperature readings. If it’s a slide scale, the scale’s arrow will point to the relative humidity. If there’s no built-in scale or slide, then consult a table or an online calculator (see Resources).
