You Have a Thermostat, But Do You Need a Hygrometer, Too?

Water vapor exists in our air, and the resulting humidity can affect us. We sweat to stay cool, but when the air's relative humidity is super high, our sweat doesn't evaporate. You know that sticky feeling when you're saturated with sweat. As a result, it feels much hotter than it actually is when humidity levels run high.

The reverse is true when there's low relative humidity in the air. Our sweat evaporates easily, due to an effect called evaporative cooling, which regulates our temperatures. But how do you monitor humidity levels around you? You can use a hygrometer to find out. There are many different types available, depending on your needs, and all of them measure humidity. That's something regular thermometers just can't do!

The Development of Humidity Sensors

Hygrometers are tools used to measure moisture content, which is the level of water vapor in the air. Many devices also measure temperature because it's an important factor used to determine humidity.

Hygrometers first became available in the 15th century in varying designs. Leonardo da Vinci was an early developer of the tool; his design measured the difference between absorbent and nonabsorbent materials. This difference was caused by atmospheric moisture absorption from the surrounding air and could be used to measure relative humidity.

Another early design was by Swiss physicist and geologist Horace Bénédict de Saussure in 1783. It measured the atmosphere's effect on the tension of a strand of human hair in the device to figure out humidity in the surrounding air. From those ancient prototypes, we can now assess a localized region's humidity level thanks to an assortment of reliable electronic devices.

The Countless Good Reasons to Measure Humidity

Today, there is a plethora of different applications for hygrometers. Like many scientific tools, there are affordable versions for casual purposes. However, if you're looking for professional-grade versions used by meteorologists, you can expect both the accuracy and price points to increase exponentially. Hygrometers play essential roles in:

weather forecasting
construction and industrial production
moisture control in a home
plant care in greenhouses
regulating humidity in residential and commercial saunas
sensitive materials storage (art, artifacts, papers, musical instruments) at museums or other archives buildings

Understanding Wet and Dry Bulb Temperature

Two common terms you'll find with regards to determining humidity are wet bulb temperature and dry bulb temperature. Dry bulb refers to the temperature you can expect to read on a thermometer. It doesn't include any content related to moisture.

Wet bulb, on the other hand, is named as such because it measures temperature using a thermometer that is wrapped in a wet cloth. Once exposed to the open air, it measures the rate at which water evaporates, calculating moisture content and relative humidity.

Types of Hygrometers

There are different types of hygrometers, too:

Mechanical hygrometer: Measures the expansion and contraction of organic materials.
Electrical hygrometers: Measures the change in electrical resistance of a conductive material. They are available in two main types, resistive or capacitive. The former measures the contraction of ceramic caused by humidity, and the latter measures electricity passed through two metal plates, which are affected by humidity.
Dew point temperature hygrometers: The most precise type, which measures actual condensation on a cooled piece of metal.
Psychrometer: Measures the difference in temperature between two thermometers, a dry bulb thermometer and a wet bulb thermometer.

Some of these devices have capacitive sensors, while others have resistive sensors. While both options serve the same function, which is to measure relative humidity, they calculate it differently. Capacitive hygrometers identify changes in electrical capacitance to detect moisture content, whereas resistive hygrometers identify electrical resistance in order to calculate the dew point.

The Benefits of Hygrometers

Hygrometers can also be useful for personal health. Dry air can be uncomfortable and air with too much moisture content can enable mold and pathogens to thrive. Inexpensive hygrometers can be used to monitor the humidity of a home, office, or workspace to improve air quality and prevent mold.

If your home has creaky wooden furniture, lots of dust and static electricity — especially when you touch a door handle or light switches — you probably have low humidity. If your home's humidity is too high, you might have mold or wet windowsills from too much condensation. The right hygrometer can control humidity and recognize where condensation occurs.

To determine your home's humidity, simply place your hygrometer in a living area away from the kitchen and bathrooms. According to ThermoPro, a manufacturer of hygrometers, absolute humidity in the home should be kept between 40 and 50 percent. If the humidity is too low, consider adding a few room humidifiers or a whole house humidifier that is installed as part of your home's HVAC system. Dehumidifiers can help you control the opposite problem.