Sensors are widely used in various fields like production, life, scientific research, and in aspects such as environmental protection, transportation, family life, and space development. They can convert non-electrical physical quantities (like speed, displacement, pressure, temperature, humidity, flow, sound intensity, and light intensity) into electrical quantities (such as voltage, current, resistance, and capacitance) that are easy to measure, transmit, and process. We usually define sensors as “devices that provide effective electrical signal output corresponding to specific measured physical quantities.”

With the advent of the intelligent era, sensors have become more irreplaceable. Miniaturized, digitalized, and intelligent sensors are rapidly becoming popular. They change our lifestyle. Many advanced sensor devices have emerged in the instrumentation market and refreshed the market application system.

Environmental testing is close to people’s daily lives. Gas sensors are common in this application area. For example, some toxic and harmful gases in the air, like carbon monoxide, sulfur dioxide, formaldehyde, and PM2.5, can seriously threaten people’s health. So, we need corresponding gas sensors to monitor the ambient air quality.

Automotive sensors are input devices for automotive computer systems. They convert various operating information during vehicle operation, such as vehicle speed, temperature of various media, and engine operating conditions, into electrical signals. Then, they transmit these signals to the computer to make the engine in the best working state. With the development of automotive electronics and automotive safety technologies, the application of sensors in the automotive field will become more extensive.

Sensors are widely used in modern household appliances. The main contents of home automation include security monitoring and alarm, air conditioning and lighting control, energy consumption control, automatic sunlight tracking, housework automation, and personal health management. Home automation enables people to have more time for learning, education, or rest and entertainment.

At present, robots are gradually replacing human work in places with high labor intensity or dangerous operations. They are also suitable for some high-speed and high-precision work. Sensors are essential tools for robots to obtain information. So, there is a greater demand and higher requirements for robot sensors.

When we go to the hospital for a checkup, we need a large number of measuring instruments to detect physical examination data. Many of these measuring instruments are operated by various medical sensors. These sensors can convert various biological information of the human body into easily processed electrical signals. They play an important role in the development and implementation of medical instruments.

In the industrial field, gas sensors are mainly used in the petrochemical industry to detect various toxic and harmful gases. The petrochemical industry is developing. The types and application scope of flammable, explosive, and toxic gases have increased. If these gases leak during production, transportation, and use, they will cause poisoning, fire, and even explosion accidents. They seriously endanger people’s lives and property safety.

In the civilian field, gas sensors have several applications. In the kitchen, they can detect the leakage of civilian fuel gases like natural gas, liquefied petroleum gas, and city gas. By detecting the gas generated when food is cooked in the microwave oven, they can control the microwave oven to cook food automatically. In houses, buildings, conference rooms, and public entertainment venues, carbon monoxide sensors, smoke sensors, ozone sensors, etc. can control the automatic operation of air purifiers or electric fans. In some high-rise buildings, gas sensors can also detect signs of fire and give an alarm.

As an important gas detector, gas sensors have developed greatly in recent years. Their applications have become more and more extensive.