What are sensors?
Sensor is a kind of detection device, which can feel the measured information and transform the sensed information into electrical signals or other required forms of information output according to a certain law, so as to meet the requirements of information transmission, processing, storage, display, recording and control.
The characteristics of the sensor include miniaturization, digitization, intellectualization, multifunction, systematization and networking. It is the primary link to realize automatic detection and automatic control. The existence and development of sensors make objects have senses such as touch, taste and smell, and make objects slowly become alive. According to its basic sensing function, it is usually divided into ten categories: thermal element, photosensitive element, gas element, force element, magnetic element, humidity element, sound element, radiation element, color element and taste element.
Main features of the sensor:
The characteristics of sensors include miniaturization, digitization, intelligence, multi-function, systematization and networking. It not only promotes the transformation and upgrading of traditional industries, but also may establish new industries, so as to become a new economic growth point in the 21st century. Miniaturization is based on micro electro mechanical system (MEMS) technology. It has been successfully applied to silicon devices to make silicon pressure sensors.
Main categories of sensors:
By purpose
Pressure and force sensors, position sensors, liquid level sensors, energy consumption sensors, speed sensors, acceleration sensors, radiation sensors, thermal sensors.
According to principle
Vibration sensor, humidity sensor, magnetic sensor, gas sensor, vacuum sensor, biosensor, etc.
Press output signal
Analog sensor: converts the measured non electrical quantity into analog electrical signal.
Digital sensor: converts the measured non electrical quantity into digital output signal (including direct and indirect conversion).
Pseudo digital sensor: the output that converts the measured signal into frequency signal or short period signal (including direct or indirect conversion).
Switch sensor: when a measured signal reaches a specific threshold, the sensor outputs a set low-level or high-level signal accordingly.
According to its manufacturing process
The integrated sensor is manufactured with standard process technology for producing silicon-based semiconductor integrated circuits. Usually, some circuits used for preliminary processing of the measured signal are also integrated on the same chip.
The thin film sensor is formed by depositing a thin film of corresponding sensitive material on a dielectric substrate (substrate). When using the hybrid process, some circuits can also be manufactured on this substrate.
The thick film sensor is made by coating the slurry of corresponding materials on the ceramic substrate, which is usually made of Al2O3, and then heat treatment to form the thick film.
Ceramic sensors are produced by standard ceramic process or some variant process (sol, gel, etc.).
After proper preparatory operation, the formed elements are sintered at high temperature. Thick film and ceramic sensor have many common characteristics. In some aspects, thick film process can be considered as a variant of ceramic process. Each technology has its own advantages and disadvantages. Due to the low capital investment required for research, development and production and the high stability of sensor parameters, it is reasonable to use ceramic and thick film sensors.
According to the measurement purpose
The physical sensor is made by using the characteristics that some physical properties of the measured material have changed significantly.
Chemical sensors are made of sensitive elements that can convert chemical quantities such as composition and concentration of chemical substances into electrical quantities. Biosensors are made of the characteristics of various organisms or biological substances to detect and identify the chemical components in organisms.
According to its composition
Basic sensor: it is the most basic single conversion device.
Combined sensor: it is a sensor composed of different single conversion devices.
Application sensor: it is a sensor composed of basic sensor or combined sensor and other mechanisms.
By action form
According to the action form, it can be divided into active and passive sensors.
The active sensor has action type and reaction type. This sensor can send a certain detection signal to the measured object, detect the change of the detection signal in the measured object, or form a signal by the detection signal producing some effect in the measured object. Detecting the change mode of the detection signal is called the action type, and detecting the response to form the signal mode is called the reaction type. Radar and radio frequency range detector are action examples, while photoacoustic effect analysis device and laser analyzer are reaction examples.
The passive sensor only receives the signal generated by the measured object itself, such as infrared radiation thermometer, infrared camera device, etc.
