Sensors are devices that receive signals or stimulate and react, and can convert physical or chemical quantities to be measured into another corresponding output device.be used forAutomatic control, security equipment, etc.In stimulus physiology, to obtainElectrical stimulationDuring this period, more electronic stimulation devices were used.
The device used for a long time is a kind of induction coil, but it is rarely used here, most of which areVacuum tubeAnd semiconductor stimulation devices.
The national standard GB7665-87 defines sensors as: "devices or devices that can sense the specified measured signals and convert them into usable signals according to certain rules, usually consisting of sensing elements and conversion elements".The sensor is a kind of detection device, which can sense the measured information and transform the detected information into electrical signals or other required forms of information output according to certain rules, so as to meet the requirements of information transmission, processing, storage, display, recording and control.It is the primary link to realize automatic detection and automatic control.
"Sensor" is defined in the new Welsh dictionary as "a device that receives power from one system and usually sends power to the second system in another form".
According to this definition, the function of sensors is to convert one kind of energy into another form of energy, so many scholars also use "transducer transducer" to refer to "sensor".
Related concepts
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The effect of the input of a sensor on the output is called the sensing coefficient.For example, for a mercury thermometer, when the temperature rises by 1 ° C, the mercury column rises by 1 cm, then the sensing coefficient of the mercury thermometer is 1 cm/° C.
When the input and output of a sensor completely form a linear relationship, the sensor is an ideal sensor.At the same time, the ideal sensor should also follow the following principles:
1. Only affected by the measured factors;
2. Not affected by other factors;
3. The sensor itself will not affect the measured factors.
IR infrared proximity/ranging;Line tracking sensor;Ultrasonic distance detection;Laser area distance measuring instrument;Indoor positioning system;Collision sensor;Emergency/protection;Band switch;Flexible sensor;Pressure sensor;Temperature and humidity sensor;Surface temperature meter;Digital electronic compass (direction);GPS satellite positioningModule;Counting&PWM generator;Gyro andAccelerometer；Inclinometer and directional indicator;Piezo piezoelectric vibration sensor;RFID Reader module;PIR object movement detection;Hall Effect sensor（Hall Effect Sensor ）；gas detector 。
type
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Temperature sensor
Temperature sensors are generally electronic components that convert temperature into electronic data.A temperature sensor made of a conductor whose resistance varies with temperature.Platinum is most commonly used, and the resistance is 100 at 0 ° COhmsElement of (Pt100).Semiconductor temperature sensors are generally integrated with amplification and adjustment circuits.crystal oscillator The oscillation frequency of varies with temperature, so the temperature can be measured very accurately[1]。
Thermocouple for measuring temperature using thermoelectric effectSurface charge densityIt changes with temperature, so its surface charge intensity can be used to measure temperature.
Pressure sensor
Pressure sensor
The pressure sensor is used to measure the pressure of liquid and gas.Similar to other sensors, the pressure sensor converts the pressure into electrical signal output when working.Pressure sensors are widely used in many monitoring and control applications.In addition to direct pressure measurement, the pressure sensor can also be used to indirectly measure other quantities, such as liquid/gas flow, speed, water surface height or altitude.
There are great differences in the technology, design, performance, working conditions and price of pressure sensors.It is conservatively estimated that there are more than 50 kinds of pressure sensors in the world and at least 300 enterprises produce pressure sensors[2]。
At the same time, there is also a kind of pressure sensor designed to dynamically measure the high speed changing pressure.Examples of applications are the combustion pressure of the engine cylinder orturbogeneratorPressure monitoring of medium gas.Such sensors are generallyPiezoelectric materialManufacturing, such as quartz.
Some pressure sensors, such as those used in the traffic execution camera, operate in binary mode, that is, when the pressure reaches a certain value, the sensor controls to turn on or off the circuit. This type of pressure sensor is also called a pressure switch.
image sensor
image sensor
Image sensor is a device that can convert visual images into electronic signals, which is mainly used in digital cameras and other imaging devices.Generally, a group of CCD orCMOS sensor(such as active pixel sensor).Color image sensors can be divided into the following categories according to their color resolution:
Bayer sensor, a cheap and most common image sensor, uses Bayer filter to make different pixels only focus on red, blue and greenSanyuanA kind of light sensitivity in colored light. These pixels are interlaced together, and then the original image is restored through demosaicing interpolation;
Foveon X3 sensor, used for some Sigma and Polaroid digital cameras.Each pixel has a triple sensor, which can be sensitive to all colors;
3CCD sensors, such as some Panasonic digital cameras, use bicolor prisms for light splitting and three independentCCD sensorIt is generally believed that image restoration has the best quality but is expensive.
Hall Effect Sensor
Hall effect sensor is also calledhall sensor Is a transducer that converts the changing magnetic field into the change of output voltage.Hall sensor is first used to measure magnetic field. In addition, it can also be used to measure physical quantities that generate and affect magnetic field, such as proximity switch, Hall multiplier, position measurement, speed measurement, and current measurement equipment.
Hall Effect Sensor
In its simplest form, the sensor acts as an analog transducer and returns a voltage directly.Under a known magnetic field, its distance from the Hall disk can be set.Using multiple sets of sensors, the relative position of the magnet can be inferred.The current passing through the conductor will produce a magnetic field that changes with the current, and the Hall effect sensor can measure the current without disturbing the current.Typically, it is integrated with the winding core or permanent magnet beside the conductor to be measured.
Normally, the Hall effect sensor is connected to the circuit to allow the device to operate in digital (on/off) mode, in which case it can be called a switch.Common equipment in industry, such as air cylinder, is also used in daily equipment;For example, some printers use them to monitor paper shortage and cover opening.When the keyboard is required to be highly reliable, it is also used in the keyboard.
Hall effect sensors are usually used to measure the speed of wheels and shafts, for example, on the ignition timing (timing) or tachometer of internal combustion engines.It is inBrushless DC motorIt is used to detect the position of permanent magnet.The wheel shown in the figure is equipped with two equidistant magnets, and the voltage on the sensor will reach the peak twice in a cycle.This setting is usually used for calibrationDisk driveRate of.
Inclination sensor
Inclination sensors are widely used in military, aerospace, industrial automation, engineering machinery, railway locomotives, consumer electronics, marine ships and other fields.Whig provides domestic users with the most comprehensive and professional product solutions and services in the world.Provide more than 500 specifications of servo type, electrolyte type, capacitive type, inductive type, optical fiber type tilt sensors.
Acceleration sensor
There are low-frequency high-precision force balance servo type, low-frequency low-cost thermal convection type and medium and high-frequency capacitive acceleration displacement sensors.The total frequency response range is from DC to 3000Hz.Applications includeMotor sportControl, automobile testing, home appliances, game products, office automation, GPS, PDA, mobile phones, vibration detection, building instruments and experimental equipment.
Infrared temperature sensor
Widely used in household appliances (microwave ovens, air conditioners, range hoods, hair dryers, toasters, induction cookers, frying pans, air heaters, etc.), medical/household thermometers, office automation, portable non-contact infrared temperature sensors, industrial field temperature measuring instruments, and electrical automation.It can not only provide sensors, modules or complete temperature measuring instruments, but also provide optical lensesASIC, algorithms, etc.
application area
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Application of sensors The application fields of sensors include machinery manufacturing, industrial process control, automotive electronics, communication electronicsConsumer ElectronicsAnd special equipment.
special equipment
Special equipment mainly includes medical, environmental protection, meteorology and other fieldsElectronic equipment。At present, the medical field is an emerging market with huge sales and considerable profits of sensors. This field requires sensors to develop in the direction of miniaturization, low cost and high reliability.
industrial automation
Inductors used in industrial field, such as process control, industrial machinery and traditional ones;Various measuring process variables (such as temperature, liquid level, pressure, flow, etc.);Measuring electronic characteristics (current, voltage, etc.) and physical quantities (motion, speed, load and strength), as well as traditional proximity/positioning sensors, have developed rapidly.
Communication electronic products
The substantial growth of mobile phone production and the continuous increase of new mobile phone functions have brought opportunities and challenges to the sensor market. The rising market share of color screen phones and camera phones has increased the application proportion of sensors in this field.In addition, ultrasonic sensors used in group phones and cordless phones, magnetic sensors used in magnetic storage media, etc. will show strong growth.
automotive industry
The key to the level of the electronic control system of modern premium cars lies in the number and level of pressure sensors. At present, an ordinary family car is equipped with dozens to nearly 100 sensors, while the number of sensors on luxury cars can be up to more than 200, usually more than 30 types, and more than 100 types.
Principle structure
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Sensors convert one form of energy into another.There are two types: active and passive.
Active sensors can directly transform one form of energy into another without external energy or excitation source.
Passive sensors cannot directly convert the energy form, but they can control the energy or excitation energy input from another input terminal. The sensors undertake the task of converting the specific characteristics of an object or process into quantities.Its "object" can be a solid, liquid or gas, and their state can be static or dynamic (that is, process).Object properties can be detected in many ways after being converted and quantified.The characteristics of an object can be physical or chemical.According to its working principle, it converts object characteristics or state parameters into measurable electrical quantities, and then separates this electrical signal and sends it to the sensor system for evaluation or marking.
developing process
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automatic control systemAble to complete certain tasks according to human design without human participation.The key lies in the introduction of feedback, which actually adds the output or state of the system to the input of the system and acts on the system together with the input of the system.The output state of the system is actually various physical quantities, including voltage, flow, speed, etc.These quantities are often different from the input quantities of the system in nature, and the range of values is also different.Therefore, it cannot be directly combined with the input, and needs to be measured and converted.The sensor just plays this role. It is like the eye and skin of the control system. It senses various changes in the control system and cooperates with other parts of the system to complete control tasks.
In order to obtain information from the outside world, human beings must rely on sensory organs.However, human sense organs are not omnipotent. In order to obtain more abundant information, further study natural phenomena and manufacture labor tools, human sense organs are not enough.As a tool to replace human senses, the history of sensors is even older than the emergence of modern science.As a weight measuring tool, the balance has been used since ancient Egypt, and has been used until now.The temperature measurement using the expansion characteristics of liquids has appeared since the sixteenth century.Inductors based on the basic principles of electricity are produced on the basis of the development of modern electromagnetism. However, with the improvement of the reliability of active components such as vacuum tubes and semiconductors, this type of inductor has been developed rapidly. Today, when it comes to inductors, it mostly refers to devices that output electrical signals.
