Sensor principle

The sensor is a detection device that can feel the information being measured, and can transform the sensed information into electrical signals or other required forms of information output according to a certain rule, so as to satisfy the transmission, processing, storage, and display of information , Recording and control requirements.

The sensors classified by the measured physical quantity are: temperature sensor, humidity sensor, pressure sensor, displacement sensor, flow sensor, liquid level sensor, force sensor, acceleration sensor, torque sensor, etc.

The passive sensor cannot directly convert the energy form, but it can control the energy or excitation energy input from another input terminal. The sensor undertakes the work of converting the specific characteristics of an object or process into a quantity.

The sensor is actually a functional block whose role is to convert various signals from the outside into electrical signals.

In order to detect and control various signals, it is necessary to obtain signals that are as simple and easy to process as possible. Only electrical signals can meet this requirement. The electrical signal can be easily amplified, fed back, filtered, differentiated, stored, and operated at a long distance.

The progress of modern sensor manufacturing depends on the development intensity of new materials and sensitive components used in sensor technology. The basic trend of sensor development is closely related to the application of semiconductors and dielectric materials.

The existence and development of sensors give objects the senses of touch, taste and smell, and make objects slowly become alive. According to its basic perception function, it is usually divided into ten categories: heat sensitive components, photosensitive components, gas sensitive components, force sensitive components, magnetic sensitive components, humidity sensitive components, acoustic components, radiation sensitive components, color sensitive components and taste sensitive components. .

The sensitive element directly senses the measured and outputs a physical quantity signal that has a definite relationship with the measured; the conversion element converts the physical quantity signal output by the sensitive element into an electrical signal; the conversion circuit is responsible for amplifying and modulating the electrical signal output by the conversion element; the conversion element and The conversion circuit generally also needs auxiliary power supply. The resistance strain gauge in the sensor has the strain effect of metal, that is, mechanical deformation occurs under the action of external force, so that the resistance value changes accordingly. Resistance strain gauges are mainly divided into two types: metal and semiconductor. Metal strain gauges are divided into wire type, foil type and thin film type. Semiconductor strain gauges have the advantages of high sensitivity (usually dozens of times that of wire and foil types) and small lateral effects.

Sensor application

With the arrival of the intelligent era, sensors have become more irreplaceable. Miniaturized, digitized, and intelligent sensors are rapidly being popularized, which in turn changes our lifestyle. Recently, many advanced sensor devices have emerged in the instrumentation market, refreshing the market application system.

In the 21st century of informatization, sensors cannot be separated. Sensors have a wide range of application fields, including electronic computers, production automation, modern information, military, transportation, chemistry, environmental protection, energy, marine development, remote sensing, aerospace, and so on. Here is a brief introduction to some commonly used sensors.

  1. Sensors and environmental protection

At present, the global air pollution, water pollution and noise have severely damaged the ecological balance of the earth and the environment on which we live. This status quo has attracted the attention of all countries in the world. In order to protect the environment, various environmental monitoring instruments made of sensors are playing an active role. Environmental detection is closer to people’s daily life. This is also an application field with more gas sensors. For example, some toxic and harmful gases in the air will seriously threaten people’s health, such as carbon monoxide, sulfur dioxide, formaldehyde, PM2.5 and other gases. A corresponding gas sensor is needed to monitor the ambient air quality.

  1. Cars and sensors

At present, the application of sensors in automobiles and the measurement of relevant parameters such as fuel allowance. It is not only limited to driving speed, driving distance, and engine rotation speed due to the increasing number of automobile traffic accidents and the hazards of automobiles to the environment, sensors are used in some new facilities. Such as automobile airbag system, anti-theft device, anti-skid control system, anti-lock brake device, electronic transmission control device, exhaust circulation device, electronic fuel injection device and automobile “black box” have all been applied in practice. It can be predicted that with the development of automotive electrical technology and automotive safety technology, the application of sensors in the automotive field will be more extensive.

  1. Sensors and household appliances

Sensors are commonly used in modern household appliances. Sensors are used in electronic stoves, automatic rice cookers, vacuum cleaners, air conditioners, electronic water heaters, hot air heaters, air dryers, alarms, electric irons, electric fans, game consoles, electronic mosquito repellents, washing machines, dishwashers, and photographs. Computers, refrigerators, color TVs, video recorders, tape recorders, radios, record players and home theaters have been widely used.

With the continuous improvement of people’s living standards, there is a strong demand for improving the functions and automation of household appliances. In order to meet these requirements, we must first use high-precision sensors that can detect analog quantities to obtain correct control information, and then control by a microcomputer to make the use of household appliances more convenient, safe and reliable, and to reduce energy consumption. Many families create a comfortable living environment. At present, the blueprint for home automation is being designed. In the future, the family will use a microcomputer as the central control device to monitor various states of the family through various sensors instead of people, and conduct various controls through control equipment. The main content of home automation includes: security monitoring and alarm, air conditioning and lighting control, energy consumption control, automatic tracking of sunlight, automation of housework, and personal health management. The realization of home automation allows people to have more time for study, education or rest and entertainment.

  1. Application of sensors on robots

At present, in places with high labor intensity or dangerous operations, robots have been gradually used to replace human jobs. ‘Some high-speed, high-precision tasks are also very suitable for robots. However, most of these robots are used for processing, assembly, inspection and other tasks, and are single-energy robots of automatic mechanical type for production. Only sensors that detect the position and angle of the arm are used on these robots. To make the functions of robots and humans closer in order to engage in more advanced tasks, robots are required to have the ability to judge. This requires the installation of object inspection sensors, especially visual sensors and tactile sensors, so that the robot can communicate through vision. Objects are identified and detected, and the senses of pressure, force, sliding and weight are generated on the objects through touch. This type of robot is called an intelligent robot, which can not only perform special tasks, but also general production, affairs and housework, all can be handled by intelligent robots.

  1. Application of sensors in medical and human medicine

With the development of medical electronics, the era of diagnosis based on the experience and feeling of doctors will end. Now, the application of medical sensors can perform highly difficult diagnosis on the surface and internal temperature of the human body, blood pressure and intracavitary pressure, blood and respiratory flow, tumor, blood analysis, pulse waves and heart sounds, and heart and brain waves. Obviously, sensors play a very important role in promoting the development of technology.

In order to improve the health and waste level of the domestic people, the reform of my country’s medical system will expand the target of medical services to all people. In the past, medical work was only limited to the center. In the future, medical work will play a role in a wide range of early diagnosis, early and remote diagnosis, and the development of artificial organs. Sensors will be more and more in these aspects. Applications.

  1. Application of sensors in industry

In the industrial field, the British DDS gas sensor represented by Shenzhen Sandat is mainly used in the petrochemical industry. Some oxygen sensors, hydrogen sulfide sensors, carbon monoxide sensors, etc. can be used in detecting various harmful gas applications. In addition, it can be used to detect organic solvents and toxic gases such as phosphorane in the semiconductor and microelectronics industries; in the power industry, hydrogen sensors can detect hydrogen generated during the deterioration of power transformer oil; and in the food industry, gas sensors can also detect meat The freshness of easy-to-fus foods such as foods; in the application of fresh-keeping of fruits and vegetables, the gas sensor detects the concentration of oxygen, ethylene, and carbon dioxide in the fresh-keeping warehouse to ensure the freshness and safety of the fruits; detects the oxygen in the exhaust gas in the automobile and kiln industry, roads There is also a wide range of requirements for traffic detection of the ethanol concentration in the driver’s breath.

At present, sensors have been widely used in various fields of production, life, and scientific research, covering many aspects such as environmental protection, transportation, family life, and space development. Sensors convert non-electrical physical quantities (such as speed, displacement, pressure, temperature, humidity, flow, sound intensity, light intensity, etc.) into electrical quantities (such as voltage, current, resistance, capacitance, etc.) that are easy to measure, transmit, and process. This component is usually defined as a “device that provides effective electrical signal output corresponding to a specific physical quantity to be measured”. For example, photoelectric sensors use photoresistors to convert light signals into electrical signals; pyroelectric sensors use thermistors to convert thermal signals into electrical signals; capacitive sensors can convert non-electrical signals such as angle, concentration, pressure, and displacement into electrical signals; The force electric sensor uses sensitive elements to convert mechanical signals such as speed and acceleration into electrical signals such as current and voltage.

  1. Detection and application of gas sensors in civil applications

In civil use, the application of gas sensors is mainly embodied in the kitchen to detect the leakage of civil gas such as natural gas, liquefied petroleum gas and city gas, and to detect the gas generated during cooking in the microwave oven to automatically control the microwave oven to cook food.

Specifically, the application of the British DDS gas sensor represented by Shenzhen Sandat in the civil field is mainly reflected in the kitchen, detecting the leakage of civil gas such as natural gas, liquefied petroleum gas and city gas, and detecting the leakage of food in the microwave oven when cooking. In order to automatically control the microwave oven to cook food; houses, buildings, conference rooms and public entertainment places use carbon monoxide sensors, smoke sensors, ozone sensors, etc., to control the automatic operation of air purifiers or electric fans; in some high-rise buildings, The gas sensor can also be used to detect the signs of fire and alarm.

Nowadays, sensors have been integrated into every corner of life. It can analyze users’ daily behaviors and increase the way users interact with the surrounding world. For example, motion sensors, temperature and humidity sensors that are frequently touched. Through some commonly used smart sensors, the convenience and safety of life can be greatly improved. With the development of the petrochemical industry, the types and applications of flammable, explosive, and toxic gases have increased. Once these gases leak during production, transportation, and use, they will cause poisoning, fire and even explosion accidents, which will seriously endanger people’s lives and property safety.

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