How to Measure Humidity

Humidity is the amount of water vapor present in the air at a particular time. There is no one standard humidity level in the air as it is determined by several factors. Temperature and geography are the main factors that determine the amount of humidity in the air.

Humidity can significantly affect your comfort because it affects important body functions like sweating. Due to this, humankind has devised his own ways of controlling humidity. The common ways of controlling humidity would include using heaters to alter the temperature of a room which in turn affects the humidity in that room. The other very effective method is using a humidity controller. This device is used to humidify or dehumidify the air. However, this control of humidity is limited only to small areas like rooms or buildings. Increased Global warming on the other hand has effect on the levels of humidity on a global scale.

There are two types of humidity.

  • Relative humidity. This is the ratio of the moisture present in the air to the maximum amount of moisture that the air is capable of holding.
  • Absolute Humidity. On the other hand, absolute humidity is the actual amount of water vapor present in a specified air volume.

Methods of Measuring Humidity

To understand humidity better it is important to know the various methods used to measure it. Here are some of the most common.

  • Using calculations. Relative humidity can be determined using calculations. However, the results have a negligible margin of error. To measure relative humidity using calculations it is important to understand that it is a function of both temperature and water content in the air. Using this method, it is measured through the following steps.

First you determine the maximum amount of water that the air can be able to hold i.e. the saturation mixing ratio.

Secondly you have to determine the actual amount of water present in the air.

Humidity will be equals to the actual amount of water present in the air divided by the maximum amount of water that the air is capable of holding.


  • Through Experiment. An experiment is a faster and simpler way of determining the amount of humidity in the atmosphere. Although it may not be as accurate as the other methods, it will still give you some reliable data. You can perform a simple experiment using two thermometer bulbs by following these steps.

First measure the temperature of one bulb and name it the dry bulb’.

Secondly wrap the other bulb with a damp rag until it is completely covered.

The third step is to spin the covered bulb until all the moisture in the damp rag evaporates.

Once dry you can read the resulting temperature of the wet bulb thermometer.

Lastly, subtract the temperature of the wet bulb from the dry bulb. Use this difference to determine the humidity using the Mollier diagram.


  • Using Hygrometer. A hygrometer is the standard device used to measure humidity. It is also one of the more accurate methods. There are different types of hygrometers depending on their application and size. However, we can classify them into two broad categories namely Analog Hygrometers and Digital Hygrometers.

Analog hygrometers are normally attached to other weather devices that usually also contain a thermometer. The idea behind the working of the analog hygrometer is very simple but still quite effective. It consists of a moisture sensitive material attached to a coil spring. The spring is then attached to a needle on a circular dial. Stretching and contraction of the material due to increase in moisture in the atmosphere forces the spring to move in a similar manner. This in turn affects the position of the needle on the dial. They are not as accurate as the digital ones but they are cheaper.

Digital Hygrometers on the other hand use electric current to determine the level of humidity. They use a sensor to monitor an electric current that reacts to changes in the level of moisture. The main advantages of digital hygrometers are that they are able to keep records of trends in humidity level and store some historical data. Another advantage is that they are way more accurate than their analog counterparts. However, digital hygrometers are more expensive.

  • Using a Customized Humidity controller. A customized humidity controller is a multifunctional device that can also be used to measure humidity. Apart from its main purpose being to control humidity, it also displays accurate and reliable data on the levels of humidity in a room. This device also has a clock and a temperature display function.


  • Using Satellites. Since the successful orbiting of the first satellite in the last century, weather forecasting has undergone a revolution. Now it is possible to forecast the weather pattern of any place on earth. The satellites are the most accurate instruments that can be used to measure humidity on a global scale. Special satellites are able to detect the exact humidity in the troposphere that helps to give accurate weather patterns around the world. These satellites are also able to track even the slightest changes in the humidity in real time.

Controlling Humidity

Although we cannot be able to control the humidity in the outside environment, we can fully control it inside our homes. This can be achieved through dehumidifying and humidifying.

A customized humidity controller brings these two functions under a single instrument while performing both more efficiently. It has a dry air’ alarm that alerts you when the air in your house becomes too dry and humidification is required. Apart from controlling humidity, it has an additional air purification feature.

Lack of enough humidity leads to dry air’ that is mostly caused by overheating a room especially during cold weather. Dry air makes it easy for you to catch colds and flu virus. It can also lead to structural damage on your house e.g. cracking of wood. Excess humidity is a more common occurrence that is caused by unavoidable daily activities like breathing and cooking. It can lead to the growth of mold and is a good breeding ground for disease causing insects like mosquitoes.

Instead of buying a dehumidifier and a separate humidifier, it would be more economical to purchase a customized humidity controller that is capable of performing both functions more efficiently.

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