The most frequently utilised environmental sensors are humidity sensors. Humidity sensors, also known as hygrometers, are a type of humidity sensor. This equipment is used to determine the actual humidity level in the air at any time or location. These devices are frequently used in conditions where air conditions are severe or where controlling air situations is a must for various reasons.



What is a humidity sensor?

A humidity sensor refers to an electronic device that detects humidity in its surroundings and converts the data into electric signals. Humidity sensors come in various sizes and functions; some are built into handheld devices (like smartphones), while some are part of larger embedded systems (such as air quality monitoring systems). Humidity sensors have wide use in meteorology, medicine, automobiles, HVAC, and industrial production.

Humidity sensors are of two categories, each of which calculates humidity using a different technique: relative humidity (RH) sensors and absolute humidity (AH) sensors. The maximum amount of humidity for air at about a similar temperature is compared to the live humidity measurement at about a similar temperature to determine relative humidity. To ascertain relative humidity, RH sensors should measure temperature. Absolute humidity, on the other hand, is measured independently of temperature.

Capacitive and resistive humidity sensors are the two most popular RH sensors. The capacitive sensor detects the capacitance (or capacity to store an electric charge) of a thin metal band positioned between them using two electrodes. The capacitance of the metal rises or falls in ratio to the alteration in humidity in the sensor's surroundings. A rise in humidity causes variation in charge (voltage), which is magnified and then sent to the embedded system for analysis. Resistive Humidity sensors work on a different algorithm. These sensors use a tiny polymer comb that grows and shrinks in size in response to the changes in humidity, which directly impacts the system's capacity to store charge.

Absolute humidity is measured using thermal humidity sensors. Thermal hygrometers, unlike RH sensors, have two probes: one for measuring dry nitrogen and another for measuring the air in the surroundings. When humidity is collected on the subjected probe, the sensor detects a distinction in thermal conductivity and calculates AH.

What is a temperature and humidity sensor?

Temperature and humidity sensors (also known as RH temp sensors) are a device that transforms temperature and humidity into electrical impulses that are easily measurable. Temperature and relative humidity transceivers on the market compute the amount of relative humidity and temperature in the atmosphere, convert it into electrical impulses or other signal types according to some rules, and output the gadget to a device or application to meet users' environmental monitoring necessities.

A humidity sensitive capacitor and a conversion circuit are the major components of the humidity and temperature sensor module. A glass substrate, a humidity sensitive material, a lower electrode, and an upper electrode make up the humidity-sensitive capacitor. Humidity-sensitive material is a high molecular polymer whose dielectric constant alters as the environment's relative humidity shifts. When the humidity in the climate alters, the humidity sensitive element's capacitance also varies. In other words, as the relative humidity rises, so does the humidity sensitive capacitance, and conversely. The sensor's conversion circuit transforms an alteration in humidity-sensitive capacitance into a voltage change, which equates to a shift in relative humidity from 0 to 100% RH. The sensor's outcome shows a linear change from 0 to 1 volt.

Do smart thermostats have humidity sensors?

Your HVAC system may have to work extra hours to resolve rapidly changing moisture levels in the atmosphere due to humidity buildup. If the humidity level rises too high, it can cause severe problems like rot and water damage. Your tado° can assist you in controlling the humidity.

tado° smart radiator thermostat, smart thermostat, wireless smart thermostat, and other devices have the Air Comfort Skill feature for a comfortable home. Additionally, it provides information about the air quality in your immediate environment and indicates ways of improving the atmosphere in your home.

After assessing the outdoor air quality levels, tado° will suggest the right time to ventilate your home. It also considers the room climate dependent on various parameters such as temperature and humidity.

Air Freshness

This card displays the current freshness of the air in your home, an overview of present outdoor air in your neighbourhood, and pollen levels throughout high pollen count durations. This information will assist you in determining when it is appropriate to air your rooms.

Outside Air

The card depicts the present intensity of the six most essential pollutants in the outside air. tado° will show the air quality index. The higher the index, the better the quality of the outside air.

Pollen Forecast

This card displays the pollen level for the present day and the pollen prediction for another two days. Allergy sufferers can see how much pollen is present in the grasses, weeds, and trees across them.

Comfort Level per room

You can also learn about the present comfort level in each room with a tado° system installed. The status in the top right corner and the tiny white mark in the graph in the room card imply this. The status will tell Pleasant, and also the white mark would be in the centre of the graph when the indoor climate is suitable.

History of Heating and Cooling Activity

In the tado˚ app's Climate Report, you can see a detailed history of your heating and cooling activity. If you have tado˚ auto assist, you could also find helpful and precise information in the Care & Protect section under Heating Activity.

Select the Climate Report icon in the top right corner of the Room Screen to get your report.

The report shows variations in room temperature, external temperature, and weather throughout the day.

Three buttons on the right-hand side of the Climate Report will provide you with additional information, including Heat Request or On/Off, Humidity, and Sunshine. 

If there is a problem with the connectivity of your tado° devices, the report will show a break in the curve for that duration.

Features Available on The Room Screen of The App

Tapping on any of the rooms from the application's Home Screen will take you to that room's display, and more data about the room's indoor environment is accessible there.

The current temperature reading, the focus set temperature, the heat request, and the humidity levels in the room are all displayed on the Room Screen.

You can set a personalised heating routine for the room by pressing the Smart Schedule icon at the top right of the screen. By pressing the Climate Report icon in the top right of the screen beside the Smart Schedule icon, you can see the room's temperature and moisture history.

Starter Kit – Smart Thermostat

Make your central or underfloor heating smart. Save energy and maximize comfort. Available in two versions: Wireless and Wired.

Learn more

What are the types of humidity sensors?

Humidity sensor measures changes in electrical currents or air temperature to determine humidity levels. Capacitive, resistive, and thermal humidity sensors are the most common types. To measure the humidity in the air, all three types will oversee minute changes in the environment.

Capacitive Humidity Sensors: The humidity sensor is a small capacitor with two electrodes and a hygroscopic dielectric layer between them. The dielectric material mostly in capacitive sensors is plastic or polymer, with a dielectric constant ranging from 2 to 15. When there is no humidity in the sensor, the capacitance is determined by this constant and the sensor geometry.

These sensors are popular for their accuracy and ability to detect a broad range of humidity levels.

Resistive Humidity Sensors: A resistive humidity sensor, also known as a hygristor or an electrical conductivity sensor, measures the resistivity between two electrodes to determine the relative humidity.

The advantage of this humidity sensor is that it is inexpensive and can swap devices. The difference between capacitive and resistive humidity sensors is that capacitive humidity sensors operate well when the sensor and signalling circuit has a considerable distance.

Thermal conductivity humidity sensors: They evaluate Absolute Humidity, so, Thermal Conductivity Humidity Sensors are also known as Absolute Humidity (AH) Sensors. Thermal Conductivity Humidity Sensors determine the thermal conductivity of both dry and humidified air.

These sensors are ideal for scorching environments and could offer a more precise reading than some other sensors.

What are the benefits of a Humidity sensor?

There are a lot of them on the humidity sensor. The humidity sensor is vital for monitoring applications' healthy, convenient, and energy-saving surroundings. HVAC, food manufacturing, agriculture, and biomedical companies rely on humidity sensors to keep their operations running. High humidity levels can hamper manufacturing processes in the air, and humidity also affects the wellbeing of the personnel.  Controlling the moisture in the air is essential to avoid such a disaster. Once your sensor detects the moisture levels, you can regulate the humidity with a dehumidifier to secure your work.

Judgement Parameters: Once you've got one, you'll want to keep an eye on how it performs. There are a few considerations that could act as a benchmark for evaluating the performance of your humidity sensor.

Accuracy: The sensor has a standard curve that ensures accuracy. In the chart, the advantages will be weighed against the disadvantages.

Linearity: It will interpret the  BFSL's distinctive value and the calculated values to calculate relative humidity.

Reliability: The sensor must be able to provide accurate readings.

How to choose a good humidity sensor?

The effectiveness and price of different temperature and humidity sensors are vastly different. So, how do you pick the best sensor for your project?

Measure Range

You must first determine the measurement range of your temperature and humidity sensors, just like the weight and temperature sensors. Temperature and humidity monitoring and control do not usually require entire humidity (0-100% RH) measurement, except for meteorological and scientific research organisations . In general, the larger the range, the higher the price; select the range that best meets your project requirements.

Humidity Accuracy

The humidity sensor's most vital metric is measurement precision. The humidity sensor advances a step or a grade for each percent rise. Since different precisions must be achieved, production costs and retail prices differ significantly.


It shows the voltage difference between the measured output voltage and the BFSL value, transformed to relative humidity.


The sensor is commonly out of sync as a result of the measurements. On the other hand, a sensor must provide accurate measurements to be helpful.


The readings from a sensor must be accurate enough to avoid drifting. The drift measurement between readings of a single quantity is known as repeatability.

Response Time

The response time refers to the time it takes to rise to 66% (rise time) or fall to 33% (fall time) of its maximum output voltage.

Where should I place my humidity sensor?

Humidity sensing is critical, particularly during the cold months that most of us are experiencing right now. When installed and used correctly, Humidity transmitters allow automation systems to detect when the air is too dry or humid for convenience. Here are a few places to install your humidity sensors.

The mounting location should be in a dry, sheltered area.

Wall Mount RH Transmitter
  • Setup the transmitter where it'll be subjected to unrestrained airflow that indicates the constrained environment's average moisture and/or temperature.

  • Install the transmitter on an interior wall 4-6 feet above the ground.

  • Avoid places with excessive moisture, fumes, amplitude, or high-temperature conditions. Examples are portable electric heaters, coffee machines, computers, photocopiers, and other devices that generate high ambient temperatures.

Duct Mount RH Transmitter
  • Place the transmitter in the duct's centre , with the sensor probe in the middle.

  • Ensure it's not near fans, corners, heating and cooling winding, dampers, or other devices that could interfere with relative humidity monitoring.

  • For proper functioning, the mounting location must have sufficient airflow. Because most duct systems have an exterior air intake, pollutants in the outside air could affect the sensor and the recurrence it requires to be re-calibrated.

  • According to the manufacturer's recommendations, the inspection of RH transmitters in the ductwork must get performed yearly.

RH Transmitter for Outdoor Use
  • The mounting location must be in a dry, contained area. For protecting sun-heated air from rising the building's ceiling and influencing the relative humidity of the sensor, the transmitter must be placed on the building's north side.

  • Give special consideration to the place of heat-generating condensing devices and building vents and fan exhausts. The heated air and conceivable contaminants related to building exhaust could affect the transmitter's precision and possibly pollute the sensor element, necessitating the preterm replacement of the unit's or sensor element.

How does tado˚ detect humidity?

The Open Window Detection feature on tado° detects if a window is open by detecting unexpected temperature changes or humidity and then turns off for a short period to save energy.

In the tado° app, go to Settings > Open Window Detection to enable or disable this Skill.

When there is an open window detection, tado° turns off for 15 minutes by default. In the tado° app, go to Settings > Open Window Detection to customise  how long tado° stays off for each dwelling unit.

Before the predefined shutoff time passes, you could even turn tado° up later in the app or on the gadgets.