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What do you know from experts | How would you choose among these 7 humidity sensors for measuring water content?

Latest update time:2024-05-08
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Humidity refers to the content of water vapor in the air, usually expressed as a percentage of relative humidity (RH). The level of humidity will have an impact on human life and the operation of electronic products. Therefore, such as meteorological observation, agriculture, industrial processes, In fields such as building management, medical equipment, food and pharmaceutical industries, humidity sensors (Humidity Sensor) that can sense humidity changes in the air are often used for humidity control and monitoring.

thermometer

Through the video of about 5 minutes , we will take you step by step to understand the internal structure and working principle of each sensor.

Humidity Sensor Types and Characteristics

There are many types of humidity sensors, each with different operating characteristics. The following will introduce you to some common humidity sensor types and operating principles.

Humidity sensitive capacitor and its equivalent form

1


capacitive humidity sensor

Capacitive humidity sensors measure humidity based on capacitance changes. This type of sensor usually has high accuracy and is relatively insensitive to temperature changes. Common capacitive humidity sensors use humidity-sensitive capacitors for humidity sensing.
Capacitive humidity sensors typically have high accuracy and are able to provide accurate humidity measurements, making them suitable for applications with high humidity requirements, such as laboratory environments or control in manufacturing processes. In addition, this type of sensor usually has a fast response time and can respond to changes in humidity in the environment in real time, which is especially important in applications that require real-time control.
Many capacitive humidity sensors operate with low power consumption, making them suitable for battery-powered applications that require long-term operation, such as those in wireless sensor networks. Capacitive humidity sensors are less sensitive to temperature changes than some other types of humidity sensors, which allows them to provide stable humidity measurements under different temperature conditions.
Some capacitive humidity sensors are able to provide measurements of both temperature and humidity, making them versatile sensors capable of monitoring both the humidity and temperature of the environment. Some models of capacitive humidity sensors are somewhat resistant to contamination and can operate in environments where dust or other contaminants are present.
As technology advances, capacitive humidity sensors are becoming increasingly miniaturized and integrated, which makes them easier to integrate into various applications, such as mobile devices, smart home devices, etc. Many capacitive humidity sensors provide a digital output, which makes reading and processing of data more convenient and easier to integrate with a microcontroller or other digital system.
Thermistor Humidity Sensor

2


Resistive Humidity Sensor

Resistive humidity sensors use hygroscopic materials. When the hygroscopic material absorbs moisture, its resistance value changes to measure humidity. Humidity sensors are usually made of materials such as hygroscopic resistors and thermistors.
The structure of a resistive humidity sensor is relatively simple and usually includes a hygroscopic material. When this material absorbs moisture, it causes a change in resistance value. Due to their simple construction, resistive humidity sensors are generally relatively inexpensive, making them competitive in cost-sensitive applications.
Resistive humidity sensors have good adaptability to different application scenarios and environments, and can still work normally under some harsh conditions. Resistive humidity sensors are capable of providing continuous humidity monitoring, making them suitable for applications that require real-time monitoring and control of humidity.
The change in resistance value of a resistive humidity sensor is usually related to temperature, so in some cases, the effect of temperature on humidity measurement needs to be considered. Resistive humidity sensors can have slower response times than some other humidity sensing technologies, especially in rapidly changing environments.
Because hygroscopic materials may be subject to age or contamination, resistive humidity sensors may require periodic calibration to ensure accuracy. Although resistive humidity sensors perform well in some applications, they may be less accurate than some other high-precision sensors.

Humistor

3


Surface Strain Humidity Sensor

Surface strain humidity sensors use a material that senses strain. When the material absorbs moisture, causing a change in surface strain, these sensors use the surface strain of the material in wet and dry conditions to reflect the humidity level of the surrounding environment.
Surface strain gauge humidity sensors are typically very sensitive to changes in humidity and can provide accurate humidity measurements. This type of sensor usually operates in different humidity ranges, making it suitable for a variety of applications. Surface strain humidity sensors typically have fast response times, allowing them to respond to changes in humidity in the environment in real time. Due to their simple structure, this type of sensor usually has high reliability and can still work normally under some harsh conditions.
The performance of surface strain humidity sensors depends largely on the sensing strain materials used . Different materials may have different application ranges and characteristics. Surface strain humidity sensors may be more sensitive to temperature changes, so in some applications Additional temperature compensation is required.
The reliability and longevity of surface strain gauge humidity sensors may be affected by the materials used and the environment and need to be considered based on the specific application. As technology advances, surface strain gauge humidity sensors are becoming increasingly miniaturized and integrated, making them easier to integrate into a variety of applications.

Other humidity sensors

4


Optical humidity sensor

An optical humidity sensor is a sensor that uses optical principles to measure humidity. It uses optical devices such as optical fibers to infer the humidity level of the surrounding environment by measuring the absorption or scattering of light by water. Common optical humidity sensors use Infrared rays, microwaves and ultrasonic waves are also used for humidity sensing.
Optical humidity sensors are usually capable of non-contact humidity measurement, without the need for the sensor to directly contact the measured object, and have high accuracy and can provide accurate humidity measurements, especially under low humidity conditions.
Optical humidity sensors typically operate within different humidity ranges, making them suitable for a variety of applications and capable of providing real-time humidity monitoring, which is especially important in applications that require fast response.
Optical sensors use properties of light, such as absorption, scattering, or reflection, to infer humidity levels. Common techniques include refractive index, fiber optic spectroscopy, etc. Compared with some other types of humidity sensors, optical sensors are relatively insensitive to temperature changes, which allows them to provide stable humidity measurements in environments with large temperature changes.

Optical sensors are generally less susceptible to external contaminants because they do not come into direct contact with the object being measured. Due to the use of optical principles, optical humidity sensors usually have better adaptability to various environmental conditions. Optical humidity sensors often require periodic calibration to ensure accurate measurements.

5


Electrochemical humidity sensor

Electrochemical humidity sensors are based on the principle of electrochemical reactions. They usually use electrodes and electrolytes to interact with moisture to measure humidity, and infer the humidity level of the surrounding environment by measuring the corresponding electrochemical parameters.
Electrochemical humidity sensors are generally very sensitive to humidity changes and can provide accurate humidity measurements. This type of sensor usually operates in different humidity ranges, making it suitable for a variety of applications. Electrochemical sensors provide real-time humidity monitoring, which is especially important in applications requiring fast response.
The core part of an electrochemical humidity sensor includes electrodes and electrolytes, where the properties of the electrolyte and the material of the electrodes directly affect the performance of the sensor. The performance of electrochemical humidity sensors may be affected by temperature changes, and accuracy at different temperatures needs to be considered. Because electrochemical humidity sensors can be affected by aging of the electrolyte and other factors, they often require periodic calibration to ensure accuracy.

Electrochemical humidity sensors are usually highly adaptable to environmental conditions, but in some extreme environments, such as high humidity or high temperature environments, further considerations may be needed about their applicability. Electrochemical humidity sensors typically have relatively fast response times, facilitating real-time monitoring and control.

6


Thermal humidity sensor

Thermal humidity sensors utilize the principle of heat scattering or thermal conductivity, usually using heating devices and sensing devices including thermocouples or thermal resistors, to infer the humidity level of the surrounding environment by measuring the conduction or scattering of heat.
Thermal humidity sensors are generally very sensitive to humidity changes and can provide accurate humidity measurements. This type of sensor usually operates in different humidity ranges, making it suitable for a variety of applications.
Thermal sensors provide real-time humidity monitoring, which is especially important in applications that require fast response. Thermal sensors are not affected by light, so they can still work well in low-light or dark environments.
Thermal humidity sensors can operate on the principle of heat dissipation or thermal conductivity. Thermal scattering utilizes the scattering effect of moisture on heat, while thermal conductivity is based on the conductive effect of moisture on heat. Thermal humidity sensors are often affected by temperature changes and may require further temperature compensation to ensure measurement accuracy. Thermal humidity sensors may require periodic calibration due to factors that affect heat conduction or scattering.
Thermal humidity sensors typically have relatively fast response times, facilitating real-time monitoring and control. Such sensors are generally unaffected by chemicals, allowing them to operate normally in environments where corrosive gases are present.
IC humidity sensor

7


Semiconductor IC Humidity Sensor

Semiconductor IC humidity sensor is a humidity sensing technology based on semiconductor materials. This type of sensor usually uses resistance, capacitance, or other electrical properties to measure the humidity in the air.

Semiconductor IC humidity sensors often include sensing devices and related signal processing circuits in an integrated circuit, giving them the advantage of being highly integrated. This type of sensor has a fast response time and can reflect changes in humidity in real time.

The output of most semiconductor IC humidity sensors is a digital signal, which facilitates easy data processing and integration into digital systems, and generally provides higher humidity measurement accuracy. Many semiconductor IC humidity sensors are designed for low power consumption and are suitable for For applications requiring long-term operation and battery power.

Semiconductor IC humidity sensors usually include temperature compensation functions to improve the accuracy of humidity measurement at different temperatures. This type of sensor is usually not susceptible to contamination and interference from the external environment and can operate stably. Due to the use of semiconductor processes, these sensors are often small and lightweight, making them easy to embed in a variety of applications.

Semiconductor IC humidity sensors can adapt to different application scenarios and perform stably under a variety of environmental conditions. This type of sensor usually has good long-term stability and is not prone to drift over time.

Humidity Sensor Selection and Design Tips

The selection and design of humidity sensors depends on the specific requirements of the application, including application needs, performance requirements, environmental conditions, etc., such as accuracy, response time, temperature range, etc.
When selecting a humidity sensor, you should first determine the needs of the application, such as accuracy requirements. Some applications may require high accuracy, while other applications may have moderate accuracy sufficient. Also consider whether your application requires fast response times. Some applications may require real-time humidity monitoring, while others may tolerate slower response times. In addition, the humidity range that the sensor needs to cover should be determined; some sensors may be suitable for a specific humidity range, while others may be suitable for a wider range.
Environmental conditions are also very important for the selection of humidity sensors, and the temperature range of the sensor in the working environment needs to be considered. Some humidity sensors may be more sensitive to temperature changes and require additional temperature compensation. Also consider whether there are harmful gases or chemicals in the application, which may affect the performance of the sensor. Some sensors are more sensitive to contamination, while others may be more tolerant.
On the other hand, the appropriate sensor type should be selected based on the application requirements, such as capacitive, resistive, surface strain, optical, electrochemical, thermal or semiconductor IC, etc. If you need to measure humidity and temperature at the same time, consider choosing a sensor with integrated functions to simplify the system.
Power supply and energy consumption are also important considerations. Consider the type of power available in the application and select the appropriate sensor. Some sensors require higher power, while others may use low-power designs. If the application needs to run for a long time or relies on battery power, consider choosing a low-power humidity sensor.
Of course, cost is still very important, and reasonable sensor selection should be based on budget constraints. The cost of different types and brands of humidity sensors may vary, and make sure the humidity sensor you choose has adequate vendor support and availability to ensure stable operation of the system.
Humidity sensors may show different adaptability in different application environments. When selecting a sensor, consider the application environment, select a sensor type suitable for that environment, and conduct field testing to ensure the performance of the sensor in actual applications.

Humidity sensor common problems and solutions

When applying humidity sensors, you may encounter some common problems that may affect the accuracy and stability of humidity measurements.
One of the most commonly encountered problems is sensor calibration, as humidity sensors require periodic calibration and may lose accuracy due to changes in environmental conditions. To perform regular sensor calibration , use reliable calibration standards. Some sensors may have automatic calibration capabilities, but periodic manual calibration is still recommended to ensure accuracy.
In addition, temperature changes can affect the performance of humidity sensors, resulting in reduced accuracy. Therefore, it is best to choose a sensor with temperature compensation to calibrate and compensate for the effects of temperature on humidity measurements. In addition, appropriate temperature control can be provided to maintain a stable temperature around the sensor.
On the other hand, sensors can be affected by dust, grease, or other contaminants that reduce accuracy. Therefore, it is necessary to clean the sensor surface regularly to avoid the accumulation of dust and contaminants. Using a dust cover or protective cover in the application is also an effective method.
Drift is also a common problem with humidity sensors. The performance of the sensor may change over time, causing drift problems. Therefore, the sensor needs to be checked and calibrated regularly to ensure stable performance. It is best to use an adjustable sensor and follow the manufacturer's calibration recommendations.
Under extremely high or low humidity conditions, some sensors may reach saturation or supersaturation, resulting in reduced accuracy. Choose a sensor suitable for a specific humidity range . Under extreme conditions, it may be necessary to use a different range of sensors or perform a reasonable calibration.

type

Application characteristics

capacitive humidity sensor

The high accuracy, fast response time and other characteristics of capacitive humidity sensors make them ideal for use in a wide range of industries and applications.

Resistive Humidity Sensor

Resistive humidity sensors remain a practical choice in some general and cost-sensitive applications due to their simplicity, lower cost, and adaptability. However, in applications requiring high accuracy and fast response times, other, more advanced humidity sensing technologies may need to be considered.

Surface Strain Humidity Sensor

Due to its characteristics of sensitivity and reliability, surface strain-type humidity sensors are suitable for humidity monitoring applications that require high accuracy and fast response, especially in scenarios where instant control and monitoring of humidity changes are required.

Optical humidity sensor

Due to its high accuracy, non-contact measurement and strong adaptability, optical humidity sensors are suitable for application scenarios that require high-precision humidity monitoring, such as monitoring in laboratories, manufacturing processes and some special places.

Electrochemical humidity sensor

Due to its high sensitivity and real-time monitoring characteristics, electrochemical humidity sensors are suitable for application scenarios that require high-precision humidity monitoring, such as laboratory environments, manufacturing processes, and some climate monitoring applications.

Thermal humidity sensor

Thermal humidity sensors have high sensitivity and real-time monitoring characteristics, and perform well in some application scenarios that require high-precision humidity monitoring, such as laboratories, manufacturing processes, and climate monitoring applications.

Semiconductor IC Humidity Sensor

Due to its advantages of high integration, real-time response, and digital output, semiconductor IC humidity sensors are suitable for various application scenarios, such as indoor climate control, smart homes, industrial automation, etc.

More product models:

HDC1080DMBR

SHT25

SHT40-AD1B-R3

BME680

HDC3020DEFR

SHT30-DIS-B2.5KS

BME280

SHT31A-DIS-B10KS

SHT31-DIS-B2.5KS

SI7020-A20-GMR

SHTC3-TR-2.5KS

SHT40-AD1B-R2

SHTC3-TR-10KS

HIH7120-021-001

SI7021-A20-IM1R

SHT45-AD1B-R2

HDC2010YPAR

SHT21S

SI7021-A20-GM1R

SHT21

SHT30-ARP-B

HDC2022DEPT

HUMIDITY-SENS-E

HIH8120-021-001

SHT30A-DIS-B10KS

HDC3021QDEHRQ1

K5_5 (200PF +/-50PF)


Conclusion

Humidity sensors are widely used. When selecting humidity sensors, you should choose different humidity sensors based on specific application requirements. Choosing the appropriate sensor type is the key to ensuring accuracy and stability to ensure the sensor's performance in different environments. working normally. In addition, during use, the humidity sensor should be calibrated and maintained regularly to maintain the accuracy of the humidity sensor.


Featured Products

Texas  Instruments

HDC1080DMBR

Sensirion  AG

SHT25

Bosch Sensortec

BME680

Sensirion  AG

SHT31 -DIS-P2.5KS

Texas  Instruments

HDC3020DEFR

Silicon  Labs

SI7021-A20-IM1R

Texas  Instruments

HDC2010YPAR

Honeywell

HIH8120-021-001

Silicon  Labs

SI7020-A20-GM1

Innovative  Sensor Technology

MK33-W  (300PF +/-40PF)




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Editor's words

Humidity sensors have wide application value in many fields such as home, industry, agriculture, archives management, smart buildings, and refrigeration management due to their high accuracy, fast response, durability, easy integration, and low power consumption. As analyzed in this article, different humidity sensors have different characteristics. Only by accurately understanding the specific needs of the application can the correct sensor be selected to meet the design requirements. What are your experiences and considerations in selecting humidity sensors for application design? Welcome to leave a message, share and communicate!


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