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Humidity Sensors

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Last Updated: May 12, 2022

All homeowners understand the need to maintain the perfect balance of humidity in a home – not too high and not too low. Too-high humidity will leave you feeling uncomfortable and ‘sticky’ as well as cause mold and mildew growth.

Even worse, a recent study published in Science Daily showed that a relative humidity higher than 60 percent could increase the rate of virus spread and absorption. On the other hand, too-low humidity can also lead to discomfort and health symptoms like dehydration.

So how do you monitor the humidity in your home to ensure it is at optimum levels? A humidity sensor is the answer to your problems. Let’s take a closer look at what it is and what it does.

typical humidity sensor
Humidity Sensor

What is Humidity?

Humidity refers to the measurement of the amount of water vapor or moisture in the atmosphere at a given temperature. Simply put, it is the amount of water vapor available in the air. When the humidity outside is at 100 percent, the air tends to get oversaturated with moisture, which results in rainfall.

You will notice that humidity levels are highly dependent on temperature. Colder air has less capacity to hold moisture, which is why winters are generally low-humidity seasons. On the other hand, during summer, when the air is warm, it tends to hold more water vapor.

Humidity affects the ‘feel’ in the air, with high humidity levels causing your skin to feel clammy and sweaty. Low humidity levels, in contrast, can cause your skin to feel dry and dehydrated. That said, the applications of humidity extend beyond how our skin feels on a given day. Humidity levels affect power consumption, industrial processes, viral infection rates, and even the structural integrity of buildings.

How is Humidity Measured?

Humidity is measured through a device called a hygrometer. The term hygrometer is scientific and might not be used regularly outside meteorological labs. In the consumer world, the instrument used to measure humidity is called a humidity sensor.

Humidity sensors act as a gauge that provides an accurate measurement of the amount of water vapor or moisture in the atmosphere. Meteorologists use larger, more complex hygrometers to study weather patterns and predict the weather, while homeowners can purchase a smaller sensor to monitor the humidity in their homes.

In most cases, humidity sensors are marketed and sold as ‘temperature and humidity sensors’ because they monitor both the relative humidity and temperature in a home. A typical household humidity sensor looks like a small, smart digital thermostat.

Note: Relative humidity is the amount of water vapor in the air at the current temperature as a ratio of the maximum amount of moisture that could be present and expressed in terms of percentage.

Humidity Levels in the Home

When the humidity levels in your home rise too high or fall too low, your living conditions can become uncomfortable. The water vapor levels in the air can also affect your furniture, walls, and the general structural integrity of your property. Low humidity levels are often linked to high viral infection spread rates, while higher levels are known to cause mold and mildew. Here is a breakdown of the effects humidity can have on your home:

· Mold and Mildew

Mold and mildew are microscopic fungi that thrive in damp areas of your home. The latter refers to the grey or white patches you will usually find on tiles, windowsills, and shower curtains. Mold, on the other hand, is the dark green or black color that tends to form on building materials. It can result in health complications, such as allergies and asthma in children.

Because mold is a fungus that digests the materials on which it grows, it can damage many features in your home if left unchecked. This includes carpets, books, and furniture. If the spread is extensive, mold can also weaken walls and ceilings, threatening the structural integrity of your house.

· Air Pollutants

High levels of humidity can worsen the spread of certain air pollutants in your household. If a building material releases toxic chemicals, such as formaldehyde, for example, it will do so more rapidly under humid conditions. You may also face an upsurge of mites, which tends to cause increased fatigue and respiratory infections among the inhabitants of an affected home.

· Damaged Walls

The walls of a building are usually fitted with air barriers to prevent warm, humid air from seeping into the surface. However, this measure is not foolproof, and high humidity can cause studs, joists, and plaster to swell then contract when the humidity drops. These changes can cause cracks in your walls – damage that could be very expensive to repair.

· Rotting Fixtures

Too much moisture in the air can penetrate the wood in your home, creating growths and stains that might eventually cause decay. This effect leads to irreversible damage to wooden fittings around your home, including furniture, window frames, and hardwood floors.

· High Cooling Costs

When the humidity is high, you will feel as if the temperature is higher than it actually is. This might cause you to crack up the air in your home, only to experience little to no change in the temperature. This constant overestimation can shoot your cooling costs through the roof.

Humidity and Your Health

Extreme humidity levels – in either direction – will affect more than your home. They can also affect your and your loved ones’ health. According to health experts, you can better avoid these health effects by maintaining the humidity levels in your home between 35 and 60 percent.

A humidity sensor will alert you when the humidity level in your house is not ideal, and your health is, consequently, at risk. Before that, however, let’s look at how humidity can affect your health:

1. Increased Risk of Infection

Your nose and throat are covered by mucus membranes designed to keep airborne pathogens out of your respiratory system. The membranes trap infection-causing viruses before they can enter your bloodstream and reach other parts of your body. Unfortunately, low humidity tends to dry out these membranes, limiting their ability to keep pathogens out of your body.

Low humidity can also irritate your nose and lips, causing them to split and expose your capillaries to pathogens. This is a more direct route for the microbes into your bloodstream. The overall effect is that you are more susceptible to viral infections.

In fact, several studies show that the flu is more common during low-humidity seasons like winter because pathogens are much easier to spread from one person to the next.

2. Dehydration or Heat Exhaustion

Sweat is your body’s main way of cooling itself. When it gets hot, your body sweats, and the sweat evaporating from your skin lowers your temperature. When the humidity is too high, the air is oversaturated with water vapor and cannot hold anymore. This means that sweat does not evaporate even though your body is still producing it. The result is heat exhaustion from the loss of minerals, salt, and water. Heat exhaustion can cause terrible symptoms like fatigue, dizziness, and muscle cramps.

If the humidity is too low, your body might get dehydrated from losing too much water to the environment. This is especially true when the temperatures are high.

3. Inflamed Dermatitis

Forms of dermatitis like Eczema can get worse due to changes in humidity. High humidity prevents sweat from evaporating, and sweat remaining on your skin can cause heat rash. Essentially, heat rash is an uncomfortable, itchy sensation that occurs when your sweat glands are clogged. On the other hand, extremely low humidity levels will drain your skin of essential oils and moisture, leading to skin disease flare-ups.

4. Poor Sleep Quality

Extremely high or low humidity can also interfere with your quality of rest. When the humidity is too high, sweat remains on your skin, causing you to feel uncomfortable and clammy. However, if you uncover yourself, the sweat will cool you down and leave you feeling cold. These two temperature changes can prevent you from really falling asleep. High humidity can also exacerbate your allergy symptoms at night and cause congestion.

In contrast, very low humidity will leave your nose and throat feeling dry. This might cause an infection or irritation or leave you feeling too parched to fall asleep. Either way, you don’t get the rest you need and end up feeling tired and groggy for the rest of the day.

5. Asthma

Humidity levels can affect the severity and frequency of asthma symptoms. According to the Harvard Annual Review of Public Health, more than 21 percent of incidents of asthma are caused by mold and dampness in homes. Since high humidity levels promote the growth of dust mites and mold, this condition can increase the amount of irritants in your house and worsen your symptoms.

Additionally, high humidity accompanied by high temperature can increase your airway resistance, making it more difficult for you to inhale. This can cause airway constriction and coughing in patients with even the mildest cases of asthma.

6. Allergies

High humidity can cause sneezing, post-nasal drip, runny nose, and congestion by increasing the amount of mucus in your throat and nose. Some of these symptoms might worsen your allergies, while others might present as a type of non-allergic rhinitis. Essentially, this is a condition characterized by chronic allergic symptoms caused by food, medication, weather, or environmental changes.

7. Chronic Throat Irritation and Skin

Lastly, extremely low humidity levels can result in an itchy nose, scratchy throat, and chronic dry skin. This is because the condition causes your body to lose more moisture than you normally would. When you swallow over and over again or rub your nose to relieve the discomfort, you may end up causing more inflammation or irritation to your mucus-deprived passageways.

Relative Humidity Sensors

As you can see, humidity levels play a crucial role in the health and comfort of you and your loved ones. This is why a humidity sensor is one of the most crucial tools you can have in your home. But what exactly is a humidity sensor, and how does it work?

A humidity sensor is an electronic device that measures and reports the air temperature and moisture levels in the surrounding environment. They will usually measure the humidity levels in whatever environment they are deployed in, which could be a confined space or even soil.

Humidity sensors are battery powered and report humidity measurements through an electronic signal, which could be displayed on the sensor (LCD Display) or sent to your mobile device (wireless sensor). They report relative humidity rather than just humidity, which is the amount of moisture available in the air as a ratio of the maximum possible amount at a specific temperature.

Relative humidity has a wide range of applications in multiple industries. It is used in comfort optimization in Smart Facilities and HVAC (Heating Ventilation Air Conditioning) systems. Moreover, meteorologists use relative humidity to predict weather changes.

Types of Humidity Sensors

There are three types of domestic humidity sensors, categorized depending on where they measure relative humidity and how they report the information. These are:

· Standalone LCD Display/Point Source

Standalone or Point Source humidity sensors are designed to read the relative humidity in certain areas of a building where the humidity levels are often the highest. A great example is a bathroom where the high water evaporation rates can cause relatively high humidity levels compared to the rest of the house.

By placing a Point Source humidity sensor in this location, you can find out if you should deploy a new exhaust fan in your bathroom to lower the humidity levels to match other rooms in your house.

· Wireless/Smart Sensor

A Smart or Wireless humidity sensor is a humidity measurement device that uses smart technology. It can usually connect to the WiFi system in your home, allowing you to view the humidity reports from your personal computer or smartphone, no matter where you are.

Additionally, some sensors will maintain records of humidity level fluctuations in your home and alert you of extreme readings through text or email.

· Humidity Meters for Home

A whole-home humidity meter is a measurement system comprising several individual sensors deployed in different locations in your home. These wireless sensors might connect to each other through any mechanism, such as Bluetooth or WiFi, to give you humidity level readings of your entire home, or just standalone. If you are looking for a more thorough approach to humidity measurement, this sensor is ideal for you.

Type of Measurement Approach

Humidity sensors can also be grouped according to the approach they use to sense and measure humidity levels in a given location. In this group, the types of humidity sensors include:

Capacitive Humidity Sensors

As the name suggests, a capacitive humidity sensor uses a capacitor to detect humidity changes in your home. The capacitor will usually consist of a hygroscopic dielectric material sandwiched between two electrode layers. Since the dielectric material is hygroscopic, it can absorb moisture from the environment and deliver readings of the relative humidity in the air.

Capacitive humidity sensors provide very stable readings over a wide range of humidity levels. However, they have a limited acting capacity in that their functionality is affected by the distance between the signaling circuit and the sensor itself.

Resistive Humidity Sensors

A resistive humidity sensor is also known as an electrical conductivity humidity sensor. This is because it detects humidity levels by measuring the change in resistivity between two electrodes. Unlike capacitive humidity sensors, these sensors are not limited by distance and can measure humidity changes through remote monitoring, where the distance between the circuit and sensor is large. Resistive humidity sensors are also more environment-friendly and affordable.

Thermal Conductivity Humidity Sensors

The last type of humidity sensor is the thermal conductivity sensor. This sensor measures humidity by calculating the thermal conductivity difference between humid and dry air. In most cases, such sensors are deployed in corrosive or high-temperature locations because they are more durable. They also provide more accurate readings than their counterparts.

Where to Put a Humidity Sensor

Where you deploy, a humidity sensor is crucial because it determines the type and quality of readings you get.

You should place a humidity sensor in the area you are concerned with monitoring. For example, if you are concerned about humidity in a bedroom, place it in there, on a dresser. If you are concerned about a leak under a sink, place it under that sink.

Maybe you want to monitor a humidor, so you would put one in there. Of course, the humidity sensor has to fit in the humidor.

Try not to put the sensor in direct sunlight or near air vents as this will skew the humidity readings. A good rule of thumb is, place the humidity sensor in an area where the air is still.

Other pointers to remember when positioning your sensors include:

Wall Mount

Place the sensor indoors on a wall at least 4 to 6 feet above the floor.

Mount the sensor in an area with unrestricted air circulation that represents the average humidity of the entire environment.

Avoid mounting the sensor in an area with excess moisture levels, such as next to a copy machine, coffee maker, or portable electric heater.

Duct Mount

Mount the sensor away from cooling or heating coils, fans, and any other equipment in your home that can affect humidity readings.

Mount the sensor so that the sensor element is in the middle of the duct.

LCD Digital Humidity Sensors

If you prefer a humidity sensor that sends relative humidity readings to an LCD display, you can try the following two top models:

1. ThermoPro TP49 Digital Indoor Hygrometer Thermometer Humidity Monitor

The ThermoPro TP49 Digital Indoor Hygrometer Thermometer Humidity Monitor has a large measurement range and can report extreme humidity levels. The LCD monitor features a face that tells you the comfort level in your home, depending on the humidity readings. By doing this, the sensor alerts you to humidity changes in your environment within seconds. You can mount it in several ways.


· Can be mounted vertically on a desk or on a wall in your home.

· Easy-to-understand interface.

· Wide range of measurements.

· Powered by one, standard AAA battery that is easy to replace.

· Battery can last between 18 and 24 months.

· Updates readings every 10 seconds.


· Some users might find the interface too simplistic.

2. ThermoPro TP52 Digital Hygrometer

This LCD Display sensor comes with a 3.3-inch display that reports the comfort level in an environment through arrows. Additionally, the display is color-enabled to ensure you can read humidity values from any distance and in any lighting. The readings are taken to an accuracy level of +-1 °C or +-23 percent Relative Humidity.


· Bright-colored LCD screen allows you to read the monitor in all lighting conditions.

· Highly sensitive sensor that measures changes every 50 seconds.


· The system uses arrows to indicate comfort level (dry/wet/comfort), which can be limiting.

Wireless Humidity Sensors

For a wireless option, try:

1. Testo Saveris 2-H1 – WiFi temperature and humidity data logger

The Testo Saveris 2-H1 WiFi temperature and humidity system offers an easy, secure monitoring experience. You can set up the system very easily by selecting a license option, connecting to the monitor through a WLAN network, and configuring the system through the Testo Cloud.

Usually, changes to humidity will be communicated to you via email (basic version) or both email and SMS (advanced option). This monitor is ideal for refrigeration units, storage facilities, and work locations.


· Has industrial applications.

· Easy to set up and configure the system.

· Alerts you of extreme humidity levels immediately.


· Some features are only available in the Advanced license option, which involves a fee.

Can also be used as a freezer alarm monitor.

2. BUN Hygro Temperature and Humidity Record Alarm System

The bun HYGRO Humidity sensor measures both relative humidity and temperature. It is cloud-based and WiFi-enabled to log data and alarm you of extreme humidity or temperature changes. Generally, the company offers a mobile or web-based app that you can use to adjust your settings and set up alarm text messages or emails that you will receive when the levels breach a set threshold.


· Has wide applicability and can be used in homes, freezers, greenhouses, etc.

· System is easy to configure through the mobile app.


· You have to set the temperature and humidity thresholds yourself,

Final Thoughts

A humidity sensor is one of the most key devices you should have in your home or factory. Its applications in the environmental, biomedical, industrial, and consumer worlds ensure that processes keep running as they should and homeowners don’t experience discomfort or health hazards in their homes.

Whether you are looking for a simple humidity sensor for your home or a more complex one for your business, remember to consider your particular needs. Both wireless and LCD digital humidity sensors have their pros and cons – you just have to know what you are looking for.