What is a Psychrometer and How Do You Use It?

In this article, we’re going to learn what a psychrometer is and how can you use it. If you’re new to scientific research, you can get expert help by talking to one of our experts. Click here to schedule an online appointment.


What is a Psychrometer?

A psychrometer is a scientific instrument that’s used to measure the relative humidity in the atmosphere. It performs its measurement using two types of thermometers:


A wet-bulb thermometer – measures the temperature by having the bulb dipped in liquid.

A dry-bulb thermometer – used to measure the temperature via exposure to the air.


By comparing both temperatures, you can determine the relative humidity of the surrounding area. You can do that by calculating the difference between the temperature variants produced by these two thermometers.


How Does a Psychrometer Work?

By reading the official definition of a psychrometer, you already have an idea about what it can do. But to give a bit more emphasis on it, here’s how a psychrometer functions:


Evaporation Basics

Once the water starts to evaporate, it starts to cool whatever surface it was on. For instance, sweat cools your body as it starts to evaporate. The air, however, can only hold a certain amount of water. The air becomes saturated when it’s humid, which means it’s filled with too much water that it can contain. Due to its incredibly high number, the water doesn’t evaporate quickly. A psychrometer makes use of this concept.



A psychrometer is the simplest type of Hygrometer.  It’s a device that measures humidity, as was already said a while ago.  It has two thermometer bulbs that measure moisture in different types of situations (refer to ‘what is a psychrometer?’ section). The dry bulb is left exposed to the air when measuring the temperature. The wet bulb, on the other hand, is covered with a cloth that’s dipped in water until it’s ready to use.


Using a Psychrometer

When you want to measure the temperature inside a room, you can do this by removing the wet-bulb from the water. Depending on the design of the psychrometer, the wet-bulb will either swing around or remain still. Once the water starts to evaporate, it will cool the web bulb. By measuring the cooling of the web bulb, the scientist can determine the amount of water that evaporates. As a result, it will tell the humidity level of the air. Moist air allows limited water to evaporate.  Dry air, on the other hand, absorbs a lot more moisture, which cools the web bulb by quite a bit.


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