Gas sensing types with various characteristics have different technical advantages.
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Gas sensing types with various characteristics have different technical advantages.

Posted Date: 2024-01-21

Electronic Enthusiast Network reports (Text/Li Ningyuan) Sensors, as an important medium for sensing the surrounding environment, have always played an important role in many fields. Gas sensing, which is closely related to our lives, has always been an important segment of the sensor industry. With the advancement of new materials, MEMS technology and electronic circuit technology, gas sensing is also constantly changing. At the same time, evolving regulations and safety standards have also put forward more stringent requirements for gas detection.

At present, according to technical principles, gas sensors can be divided into various types such as semiconductor gas sensors, catalytic combustion gas sensors, electrochemical gas sensors, and optical gas sensors. In the application of gas sensors, semiconductor, electrochemistry, and optical technology schools are the main ones.

Extensive Measurements in Semiconductor Gas Sensing

Semiconductor gas sensing is similar to temperature detection using thermistors. It is a gas sensor that uses semiconductor gas sensors as sensitive elements. It is the most common gas sensing method and accounts for almost half of gas sensing.

Resistive semiconductor gas sensors, like other resistive sensors, use the change in resistance of a semiconductor when it contacts gas to detect the composition or concentration of the gas. However, not all semiconductor gas sensors are resistive. Non-resistive semiconductor gas sensors use the adsorption and reaction of semiconductor components to gases to change certain characteristics of the semiconductor to directly or indirectly detect gases.

Generally speaking, resistive semiconductor gas sensors usually have high sensitivity, small size, fast response time and recovery time. In addition, this sensor type has been developed very maturely and the cost is very low. Therefore, this type of gas sensor is on the market. Sensing is mainstream.

Non-resistive types mainly include junction type, MOSFET type, and capacitive type. They are characterized by strong selectivity for gas elements. For example, Pd is selective for hydrogen, which means that this type of sensor is very selective for a certain gas element. The detection of gas is very targeted. Non-resistive gas sensing is often used in applications that require strong selectivity, and it is also easy to use and integrate.

Electrochemical gas sensing functions tend to be diverse

The electrochemical gas sensor catalyzes the gas to be measured, causing an oxidation-reduction reaction on the electrode surface to generate current, so its power consumption is naturally lower than other sensors. Of course, its popularity can be attributed to good linearity and decent resolution. The advantage of linearity makes it convenient to complete low concentration monitoring and subsequent calibration, and can achieve quantitative detection well.

In practical applications, electrochemical gas sensing exhibits good sensitivity and selectivity, playing a crucial role in multi-gas monitoring. Similarly, previous electrochemical sensing has also produced some commonly criticized problems, such as short service life and cross-sensitivity to other gases.

However, with the continuous development of sensing element technology, these problems have now been solved well. Targeted detection of target gases has reduced many cross-sensitivity concerns, although it must be acknowledged that electrochemical gas sensing is still worse at cross-sensitivity issues than other gas sensing types.

Under the current trend of integration, more hardware functions and more algorithms are embedded in sensors, making multi-gas monitoring applications more suitable.

Complex but highly precise optical gas sensing

Optical technology is naturally an indispensable genre in gas sensing. Using the absorption, scattering, and penetration characteristics of light, the gas concentration is converted into optical signals and displayed intuitively. Optical gas sensing has fast response speed, high sensitivity, and high precision. However, no matter which optical principle is used for sensing, the technical difficulty will be higher and the price will be more expensive. In terms of market share, it is also compared with the above two. or lower.

At present, the mainstream optical gas sensing types include infrared absorption type, spectral absorption type, fluorescence type, and optical fiber chemical material type. Taking infrared as an example, when a gas is irradiated by infrared rays of the same frequency, infrared ray absorption will occur, causing changes in infrared light intensity. By measuring the change in infrared intensity, the gas concentration can be measured.

This kind of sensing can effectively distinguish gas types, has strong anti-interference ability, and can accurately measure gas concentration. Nowadays, optical gas sensing is developing rapidly. With the advancement of process technology, its cost will gradually decrease, and the advantages of high precision will be utilized in more applications.

summary

For different application scenarios, selecting appropriate gas sensors based on different types of sensing characteristics can better achieve detection. In addition, from the perspective of the development of the entire gas sensing industry, miniaturization and low power consumption are clear industry development trends. How to integrate as many functions as possible into sensing is also a key point for differentiation.


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