What Is A Humidity Gauge And How To Use It?

Humidity is the amount of water vapors in the air. Having air with the right humidity is extremely important as it helps you feel comfortable. If the air is too dry or too moist, you will feel uncomfortable. Higher humidity will most likely make you feel warmer. In contrast, low humidity will make you feel cool without the temperature ever changing. 

You can use a humidity gauge or a hygrometer to measure this humidity. It is a scientific instrument that can help you gauge the air’s humidity level. Measuring humidity is extremely important as it can affect your environment, health and skin conditions, and even your breathing problems. They are generally used in various places and can be extremely useful, provided that you choose the right one. 

What is a Humidity gauge?

closeup of a humidity gauge.

A humidity gauge, also known as a hygrometer, is a device used to measure the relative humidity of the air. It typically displays the measurement as a percentage, with 100% indicating that the air is completely saturated with water vapor and 0% indicating that the air is completely dry. There are several types of humidity gauges, including analog and digital versions, and those that measure temperature. 

This device is used to measure humidity, which is the measure of water vapors in the air around you and is one of the variables often measured in basic meteorology. There are several kinds of humidity that are measured, but the most common one is relative humidity. It is an indirect way to calculate how much water vapors are in the air compared to what the air can hold at maximum at any given time. 

There are two main types of hygrometers in terms of function: analog and digital. 

Analog Hygrometer

An analog hygrometer uses a composite coil consisting of a thin metal strip, which is bonded to a moisture-absorbent hygroscopic material. This material is usually a paper polymer. When this strip absorbs moisture, it tends to expand while the metal strip retains its shape. This causes the coil to bend and rotate, and the needle on the dial starts to move and indicates the relative humidity. If the weather is dry, the moisture will evaporate from the material, and the coil will contract. 

Digital Hygrometers

A digital hygrometer uses a capacitive or resistive sensor to gauge relative humidity. There are differences between the electrical properties of the two, but they work by the same general principle. In both types of hygrometers, electricity flows through a small, moisture-absorbent material. This material is exposed to the air, and as the saturation levels of the material change, the electrical properties also change. 

Due to these changes, the material will absorb more water vapors. The changes and measurements of electrical properties will show up on its display, allowing you to note the humidity level.

Hygrometer Working Principle

A digital hygrometer measuring temperature and humidity levels.

A regular hygrometer works on the principle of evaporative cooling. This is when water evaporates from the surface, and the surface becomes cold because the water molecules absorb heat from the surface in order to evaporate. When this occurs, the wet bulb exhibits a lower temperature than the dry bulb. 

When the air is dry and the humidity is low, evaporation rates increase, causing the wet-bulb temperature to decrease. On the other hand, when the atmosphere is humid, the temperature of the wet bulb does not decrease as much because the evaporation is low. 

When humidity is at 100%, the dry and the wet bulb will show the exact same temperature. This is due to negligible water evaporation from the wet bulb, due to which no cooling effect emerges. 

Types of Humidity Gauges 

A digital hygrometer placed near a window sill to measure temperature and humidity.

A large variety of humidity gauges or hygrometers are available on the market. Here are some of the most common ones. 

Type of Hygrometer


Capacitive Hygrometer

A capacitive hygrometer is a type of electrical hygrometer that measures the electrical charge between two plates. As the humidity changes, so do the charge, allowing the device to measure the relative humidity.

Resistive Hygrometer

Resistive hygrometers are electrical hygrometers that measure the change in resistance that occurs as electricity passes through a ceramic substance. As the air becomes moister, more water vapors condense in the ceramic substance. 

Thermal Hygrometer

Thermal hygrometers detect the change in thermal conductivity of the air due to changes in humidity and measure it. This sensor measures absolute humidity as compared to relative humidity.

Mechanical Hygrometer

Mechanical hygrometers rely on an organic substance that contracts and expands as the humidity changes. Such materials can include human hair. The contraction and expansion of these materials can cause the needle on the dial to move, and you will be able to measure the humidity.

Dew-point Hygrometer

Dew-point hygrometers are the most precise hygrometers you can buy. They are designed to be able to detect even the smallest amount of moisture. These hygrometers contain a polished metal surface, and as humidity rises, moisture starts to condense on the surface. This allows the instrument to measure the current humidity.


A psychrometer is the most basic kind of hygrometer. It uses two bulbs, one dry and one wet. When humidity causes evaporation to occur in the wet bulb, the temperature lowers. This causes a difference in temperature between the two bulbs, which is used to calculate the humidity levels.

How To Measure Humidity

A woman adjusting an indoor hygrometer

Once you have chosen a hygrometer that measures the humidity level, you must know how to read and interpret the results. There are two main types of hygrometers, digital and analog.

Before you start to gather readings, you must install the hygrometer accurately. The best place to install a hygrometer is 5 ft above the ground, and it is at this level that the readings are the most precise. Ensure that the hygrometer is away from sunlight or air humidifiers, as it may affect its reading. You should also keep it away from your bathroom and any other heat source.

Digital hygrometers are much easier to use as they show the humidity percentage on the digital screen. If you use an analog hygrometer, you must ensure that you accurately read the figure at which the needle points.

Once you have hung the hygrometer, wait five minutes to allow it to adjust to the air around it. Digital hygrometers need to be turned on, whereas most analog hygrometers are designed to take the reading automatically. 

In five minutes, the reading should become steady. If it does not stabilize, try moving it around. Once the hygrometer rating stabilizes, you should note it down and add a percentage sign to it.

If your hygrometer shows a rating of 40 to 50% humidity, it is a comfortable rating for indoors. You will most likely not feel any moisture in this humidity, and it won’t dry out your throat and nose. If your moisture is below 40%, you will most likely feel that the air around you is dry. Your skin will feel tight and flaky, and your hair may be static. Some people also find it hard to breathe because of soreness in their noses. Such humidity levels are mostly experienced during winter months, but you can bring the humidity up by adding a humidifier.

If the hygrometer shows ratings over 60% indoors, the rating is too high, and you will feel the air is moist and sticky. Additionally, you may feel constantly damp and may even sweat more. High humidity is not ideal as it can lead to mold and increase the number of allergens in your home. 

What to Check in a Humidity gauge

A rounded hygrometer measuring the temperature and humidity.

When purchasing a humidity gauge, there are various factors that you need to look out for. This includes why you are purchasing a hygrometer, its power, accuracy, and more. Here are a few factors you should consider when buying a humidity gauge.


Since the main task of a humidity gauge is to measure humidity, it must be accurate. The accuracy you need depends on your use. If you plan on using it in greenhouses, you may want a very precise meter. On the other hand, if you will use it indoors with an indoor thermometer, you can make do with a less accurate but inexpensive device.

To check the accuracy, look for the ±% RH rating. This is the margin of error of the hygrometer. If you want a very accurate sensor, you should purchase one with a margin of ±1% RH rating. Try not to buy one that has a very high ±% RH rating. For regular use, ±4% RH rating is sufficient. 


Make sure the humidity gauge is properly calibrated before use. Many hygrometers come with a built-in calibration feature or can be calibrated using a salt solution.


When purchasing a hygrometer, ensure that it is reliable. This means that it provides consistent reading and shows a stable figure. If the needle constantly moves around or offers an entirely different figure throughout the day, then the hygrometer is unreliable. Ideally, the measurement should not drift too far from the first measurement. However, you may see slight differences since humidity changes throughout the day.

Sensor Type 

Different types of sensors are used in hygrometers, such as capacitive or resistive sensors. Each type of sensor may have different accuracy and sensitivity, so selecting the right sensor for your application is important.


When purchasing a humidity gauge, one of the most important things you should consider is what you will use it for. This is essential as it will determine the kind of hygrometer that will suit you best. If you plan to use a hygrometer indoors, you will not need as much precision. If you intend to use it outdoors, you will most likely need a specialized hygrometer that will record a much more accurate reading. 

Commonly humidity gauges are used in cigar humidors to keep the cigars full of flavor and fresh in instrument cases. Suppose you plan to place a hygrometer in a cigar case. In that case, you will most likely need an extremely accurate and small hygrometer. Such devices are usually quite expensive and high-quality.

You may also want to protect your musical instruments from moisture damage. So, putting a hygrometer in its case can be a great way to increase its longevity. In such situations, you will need a very accurate hygrometer that can measure even the smallest changes. 

One thing that you need to take care of is to place the hygrometer in an area where the temperature and humidity are stable to get an accurate measurement. Avoid placing the hygrometer near sources of heat or moisture, as these can affect the accuracy of the measurement.


Humidity and temperature are closely related, so it’s important to take temperature into account when measuring humidity. Some hygrometers have built-in temperature sensors, while others may require an external temperature sensor.

Power Source and Battery Life

If you are in the market for a hygrometer, you should consider whether it needs to be plugged in or uses batteries. Battery-powered hygrometers are excellent if you plan to move your device around a lot. Still, if you want to hang it in one place, you can opt for a hygrometer that is plugged into a socket. 

Suppose you purchase a battery-powered hygrometer. In that case, you should check its expected battery life and ensure that it lasts long enough for you to use it freely without having to change the batteries or charge them very regularly. 

User Interface

When purchasing a hygrometer, ensure that it has a user-friendly interface. The values should be displayed clearly, and you should be able to read them easily. Many hygrometers have a companion app that you can use to navigate the device and utilize it efficiently and easily.

What is a Hygrometer Used For?

A hygrometer has an extensive range of applications. You can use it to monitor your home’s humidity to avoid illnesses in offices, industrial spaces, meteorology stations, and even in greenhouses. Here are some of the most common uses for a hygrometer. 

Weather Observation 

Besides other measurements commonly taken at a meteorology station or a personal weather station, humidity is a highly vital weather measurement. It can be extremely helpful in determining the chances of rainfall, dew, and fog. Additionally, it is used to tell how it feels outside because higher humidity can make you feel hotter than usual, and low humidity can make you feel cold. This is why humidity is taken as an essential factor when measuring the heat index. 


Hygrometers are used in agriculture to monitor the humidity levels of soil and crops, which can impact the growth and yield of plants.

Indoor Climate Control

Hygrometers are used in indoor environments, such as homes, offices, and museums, to measure humidity levels and to ensure that the indoor climate is comfortable and healthy.

Manufacturing and Industries

Hygrometers are used in manufacturing and industrial processes to ensure that humidity levels are appropriate for the production of certain products, such as pharmaceuticals, electronics, and food.


How do I know if my humidity gauge is accurate?

If you are unsure about the accuracy of your hygrometer, you can try out the towel test. This includes dampening a towel, unwrapping it, and reading the humidity on your device. If it is accurate and perfectly calibrated, the reading will be precisely 100%.

Are digital hygrometers better than analog hygrometers?

Yes. Digital hygrometers are the best because they are the most accurate and provide highly accurate humidity readings. 

What is average humidity?

According to healthcare professionals, average humidity levels are between 30% and 50%.


Hygrometers are helpful devices that allow you to know the humidity levels in a particular area. Having the correct humidity level is extremely important, as low humidity can make you feel cold and itchy. In contrast, high humidity will make you feel sticky and hot.

When purchasing a hygrometer, you must consider what you will be using it for. Since there are so many different applications of a hygrometer, knowing its purpose will help you choose one that is tailored to your needs.