Using a Weather Hygrometer as a Relative Humidity Meter

The amount of moisture that is present in the air is also called the relative humidity level. All air has some level of moisture in it, but the more moisture that is contained in the air, the more uncomfortable it feels to the skin. In addition, high humidity levels in the home can lead to more serious moisture problems such as the growth of mold and mildew.

What is a Home Hygrometer?

A very easy way to test the humidity levels in the home or outside air is by using a relative humidity meter called a mechanical hygrometer. A mechanical hygrometer contains a wet bulb thermometer and a dry bulb thermometer to measure the air temperature. Together these readings provide the wet bulb depression number, which is then converted to the relative humidity level.

Setting up a Home Hygrometer

To setup a home hygrometer, first remove the water bottle that is located at the bottom of the hygrometer by twisting it until it comes free. Then fill the bottle with tap water up to the neck of the bottle. Place the water bottle back onto the hygrometer by turning the bottle clockwise until it is secure.

Hang the top loop of the home hygrometer in a location where the hygrometer bottom does not touch anything. The location should be shady if it is outdoors since direct sunlight can interfere with the hygrometer’s readings. Allow the hygrometer to sit undisturbed for five to ten minutes to acclimate to the air.

Reading the Wet Bulb Thermometer and Dry Bulb Thermometer on a Home Hygrometer

Write down the temperature reading on the wet bulb thermometer as well as the reading on the dry bulb thermometer. These thermometers are usually labeled as “wet bulb” and “dry bulb,” but the wet bulb thermometer is also identifiable by a piece of wet cloth over the end of the thermometer. Subtract the wet bulb thermometer temperature from the dry bulb thermometer temperature to reach the wet bulb depression number.

Determining the Relative Humidity from Home Hygrometer Readings

Take the wet bulb depression number, the wet bulb thermometer temperature and the dry bulb thermometer temperature from the hygrometer and look them up on a hygrometer calculation table. This table converts the wet bulb depression number into the relative humidity level of the air.

Using a relative humidity meter like a home hygrometer is an easy way to learn about the environment and solve home moisture problems.