Humidity Sensors: Everything You Must Know Before Buying One In 2024
By While building a new house with home automation in mind or even technologically advancing your current house, installing humidity sensors is necessary for smart folks now.
As the name suggests, humidity sensors are devices that can accurately capture and record the current humidity level in your room. Installing a humidity sensor is better for more humid cities that get a high amount of rainfall.
This is also why ACs have an inbuilt humidity sensor that detects and cleans your in-room humidity to make your room cool and cozy.
However, what’s the science behind the working of a humidity sensor? Moreover, if you go to the market to buy one, how will you choose which one will be the best for you?
If you want answers to all these questions, read this post till the end.
What Is a Humidity Sensor?
A humidity sensor (also known as a hygrometer) is a device that can measure the surrounding humidity in the atmosphere. In addition to the humidity level of the atmosphere, it also measures the current temperature.
People are now installing humidity seniors in their rooms to make their lives more comfortable. A high humidity level in your room means too much moisture in the air. This will make you feel uncomfortable and sweaty. Therefore, installing humidity sensors will let you measure your room’s humidity level and temperature.
Types of Humidity Sensors and Their Uses
There are three broad types of humidity sensors that you can buy from the market in 2024. They are:
1. Capacitive Humidity Sensors
Capacitive humidity sensors are the most commonly available humidity sensors in the market. These humidity sensors use capacitive sensors, which can measure the relative humidity in the air accurately from 0% to 100%.
These sensors use a thin metal oxide strip, which fits between porous and standard platinum electrodes. This allows the electrical capacity of the metal oxide to change when the humidity and temperature of the room change.
Capacitive humidity sensors are the most commonly available since their circuits and designs are easier to make than other humidity sensors. Moreover, unlike other sensors, these can accurately record temperatures as low as 0 degrees Celsius–something other sensors fail to do.
Furthermore, you will most commonly find capacitive humidity sensors inside most commercial and residential buildings. You will also find them inside vehicles, weather stations, laundry machines, ovens, refrigerators, food processors, HVAC systems, and more.
| Pros | Cons |
|---|---|
| • They can accurately detect a wide range of relative humidity • It produces a linear output voltage • The measurements remain relatively accurate and stable over many years • Low maintenance • Affordable market prices | • The distance between the signaling circuit and the sensors is big, which makes measurements laggy • The accuracy of the humidity measurement decreases when relative humidity falls below 5% |
2. Resistive Humidity Sensors
Unlike capacitive humidity sensors, resistive humidity sensors don’t use a thin metal oxide strip between electrodes. Instead, these sensors make use of ion salts. The ions in salts are unique tools for measuring the electrical impedance of atmospheric atoms.
Resistive humidity sensors have four hygroscopic conductive layers. A substrate is placed inside two electrodes, generally made of gold, platinum, or silver. Moreover, a glass or ceramic substrate on the bottom layer gives extra protection to the substrate and electrodes.
Therefore, whenever the humidity of the room changes, the resistance stems from the electrodes on both sides of the salt. In addition, there is a unique mechanism inside these sensors that measures the resistance and helps ascertain the room’s humidity.
However, resistive humidity sensors are less readily available than capacitive humidity sensors. You will commonly find resistive humidity sensors in industrial, residential, and commercial places.
| Pros | Cons |
|---|---|
| • They are cheap • These sensors leave a significantly lesser carbon footprint • They are highly interchangeable since they have no set standards for calibration • They are perfect for remotely monitoring humidity since the distance between the sensor and the circuits can be large | • The ceramic or glass bottom acts as a protector since the sensors get easily damaged due to contaminants • These sensors are not optimized for measuring relative humidity below 5% |
3. Thermal Humidity Sensors
Thermal Humidity Sensors are the newest type of humidity sensors on the block. While capacitive and resistive humidity sensors might have similarities in their operation and designs, they are entirely different.
Moreover, unlike the other two types of sensors, this sensor measures the absolute humidity of the room rather than relative humidity. It calculates the difference between dry air and humid air’s thermal conductivity.
Thermal humidity sensors have two thermistor elements matching NTC (Negative Temperature Coefficients). Therefore, one sensor (generally encapsulated in a dry nitrogen case) has ventilation holes that meet the atmosphere. The other sensor is the same, without any ventilation holes to keep it airtight.
When you switch it on, electricity passes between both thermistors. This causes the thermistors to heat up due to resistive heating. In addition, when the thermistor exposed to the humid atmosphere heats up, its conductivity changes. Therefore, this measures the resistance (relative humidity) difference between both thermistors.
While these sensors are relatively new in the market, you will most commonly see them in ovens, drying machines, kilns, and industrial food dehydrators. Therefore, these are not installed in your home or workspace.
| Pros | Cons |
|---|---|
| • These humidity sensors are highly resistant • These sensors are best used in industrial places with high temperatures and corrosive substances • They are more accurate than both capacitive and resistive humidity sensors | • They are not suitable for installation in houses and commercial spaces • Exposure to thermal gases (other than Nitrogen) can cause the humidity readings to be inaccurate |
How To Select The Right Humidity Sensor For Your Needs?
Now that you know what humidity sensors are, their different types, and how they work – how do you choose the suitable humidity sensor for your needs?
Therefore, if you wish to install humidity sensors in your home or your workplace, consider these factors before buying and installing one:
1. Accuracy
All humidity sensors follow a calibration curve. This curve has a 9-point system, where a score corresponds to the accuracy of the sensors. Typically. Most humidity sensor boxes mention this score on their back.
Therefore, check the score when you buy one. A higher score will always be better – and more expensive as well.
2. Interchangeability
If the internal sensors of the humidity sensor can be interchanged, consider it a good buy. Moreover, if the sensors are not interchangeable, it may lead to vibrations, which will incur additional costs over time for calibrating the sensor.
3. Condensation
Since humidity sensors have a lot to do with condensation at higher humidity levels and temperatures, you must buy sensors that are more resistant to condensation. This is because higher condensation on the sensors will damage them over time, which forces you to install condensation-resistant filters.
4. Power Consumption
Some humidity sensors will draw more power, while others will draw less. Typically, the more expensive they are, the more electricity bills you will save over time. Therefore, it’s best to check the back of the box to see how much power it costs.
However, remember there’s no harm in choosing a less energy-efficient sensor if you cannot afford a better one.
5. Response Time
Typically, the time a sensor takes to rise to 66% (rise time) or fall to 33% (fall time) of maximum output voltage is known as the response time.
Every humidity sensor has a response time, which refers to the rise and fall in maximum output voltage. Therefore, check whether the sensor has a 66% rise time and 33% fall time.
Conclusion
With the rise of IoT and smart home devices, installing a humidity sensor in modern homes has become an intelligent choice if you wish to lead a smart and comfortable life. Since it helps you measure the temperature and humidity of the room, you can adjust the AC settings accordingly.
Thanks for reading this post! If you have any questions, please ask them in the comments section below!
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