The use of natural physical or biological characteristics to detect external information, sensing components continue to develop under the progress of science and technology, combined with human knowledge accumulated in science, physics, medical, and now the sensor is not only a tool for human to explore knowledge, but also a combination of communication, Internet of things, cloud massive data calculation, to provide more convenient services in life.

　　Observation of the current sensing technology, the development has been mature light application, sound, dynamic, pressure and other sensors, is still in the development stage of biological cells, brain wave and other sensors. Combine these sensors to design an application device into life, and develop an intelligent device that can make independent judgments and actively provide decision-making services. How does sensing occur if human's five senses are used as a comparison?

　　The progress of nanotechnology also makes the sensor more accurate and subtle, from movement, blood flow, to brain wave detection and operation, just like many movie complex, the future of electronic and machine equipment can not only exceed the range of human sensing, but also more instant analysis and judgment, and closely combined with people's life, touch, smell, taste three sensing methods, the future has a lot of room for development. It is the focus of research and development of scientists at present.

　　Tactile sensors

　　Touch panel is the most important product of tactile sensing, recently began to become popular "fingerprint identification" technology, is also an application of tactile sensing, fingerprint identification generally uses capacitive touch screen, used in security systems, crime detection, and later placed into smart phones, applied in fingerprint locks, personal authentication and mobile payment schemes.

　　If the sense of touch is further extended to the ability to sense pressure, temperature, and surface texture like skin, it can be applied to robots. The robot will have a layer of simulated skin that will help certain types of robots to work with touch, such as improving the accuracy of grasping objects. This electronic skin technology is also trying to be used in mechanical prosthetics, which have no sense of touch, or skin grafts. Tactile sensors are constantly being developed from the perspective of biomimetic properties.

　　Gas sensor

　　Gas sensor applications are often used for alcohol detection, flammable gas detection, environmental gas detection, etc., in the environmental air detection can be used for indoor air quality detection, with temperature, humidity, barometer to form intelligent air conditioning system, active adjustment of indoor and car space air quality, and achieve the purpose of energy saving and safety maintenance.

　　The gas sensor is made by heating the oxide and absorbing the gas on the surface, and then catalyzing the change of resistance to produce the sensing signal. The components used to detect different gases are slightly different, so at present, a single sensor is usually limited to the detection of a specific type of gas, such as flammable gases, carbon dioxide, polluting gases, hydrogen, etc., also known as "electronic nose" or "olfactory sensor".

　　In the future, olfactory sensors using semiconductor processes will not only have good sensitivity, fast response, good stability, but also be easy to maintain; Used in the medical field, there are currently semiconductor gas sensors that detect the concentration of carbon dioxide to detect whether patients are infected with Helicobacter Pylori and cause gastritis and stomach ulcers. Studies in Europe, the United States, Japan and other countries have found that when the human body is sick, the concentration of specific components of the gas in the breath will increase. If such breath smell sensors can be miniaturized and integrated into mobile phones, users can use mobile phones to make health diagnosis and grasp daily health status.

　　A biological sensor

　　General sensing technology (optics, pressure, etc.) is used to identify biological features, which is called Biometric technology. Different from Bio Sensor, it is directly detected by the chemical reaction of related biomolecules. Both of them are methods to measure biomass. The latter measure data more accurately, but it has a long way to go before it is commercialized.

　　Bio-metric technology refers to the analysis of human characteristics such as face, fingerprint, and iris recognition, such as fingerprint recognition. It is mainly used to measure basic physiological signals such as heartbeat, heart rhythm, blood oxygen concentration and blood pressure through light sensors, electric currents, magnetic forces or electromagnetic waves.

　

　　Based on the technological progress of various non-biological sensors, and the programmer through the algorithm to measure a variety of physiological signals, there is a certain degree of measurability, by its infrared IR penetration is slightly stronger than visible light, can measure the surface temperature of the human body and the subtle changes in the blood for analysis. However, most of the measurements, if they are to be used at the medical level, to achieve higher accuracy as a preventive diagnosis of disease, still need to rely on biological sensors.

　　Bio-sensor is a sensing method that uses the interaction of biomolecules to sense, from measuring physiological changes to analyzing more biological elements. Due to the complexity of the biological background values measured (such as blood cells, proteins, antibodies), and the high specificity of biological elements, the detection process is usually complicated, and it is a challenge to make a sensor that can be commercialized by a single device. The sensing mode of existing commercial devices is usually to add biological molecules to the front of the sensor (probe). After interacting with the test object, it is converted into an electronic signal by a conversion element.

　　The selection of bioacting molecules is quite unique, and a biosensor can usually only measure a few specific bioagents, which is in part similar to the development of olfactory sensors. In addition to medical use, in the research and development of food and quality control, there are also the development of food analyzer, and taste sensor, taste sensor can respectively sweet, salty, sour, bitter, spicy and other five basic taste numerical, food analyzer can detect the composition of food.

　　The smart water cup launched by Vessyl can not only recognize the water or the kind of beverage in it immediately, but also assist calorie calculation and health management through mobile phone App. The blood glucose test method most needed by patients with diabetes mellitus is now also using body fluid detection, which is a great benefit to diabetic patients compared with the method of blood collection in the past. The development of contact lenses by Google X is to detect blood sugar with tears, and the miniaturization and commercialization of biological sensors will be the future development direction of remote medical treatment and personal health management.

　　A brain wave sensor

　　Our brain is made up of billions of active neurons, about 170,000 kilometers long if the Axon of the nerve is connected together, and when these neurons interact, you can measure the electrical impulses emitted by these chemical actions. The cryptographic interpretation of brainwaves is quite difficult, so the progress of brainwave sensors is not great at present. In the future, with the development of brainwave sensing, we may be able to move objects, turn on the TV, and even communicate with pets with our minds.

　　A light sensor

　　The principle of the light sensor is to convert the received light waves into telecommunication signals by the light sensitive element. Light sensing is also the most widely used sensing method, the main range is mostly concentrated in the naked eye visible light (380nm~780nm) near the frequency band, due to light reflection, refraction and other characteristics, the sensor can be emitted from the transmitter light, and then by reflection from the receiving end to detect the change in wavelength, known as active light sensing. If only the receiver directly measures the external light energy, it is passive light sensing.

　　Sensing light spectrum

　　Light sensors can be roughly classified into infrared light sensors, ultraviolet light sensors, image sensors, depth sensors.

　　Infrared light sensor

　　Infrared is a safe light that cannot be seen by the naked eye, so it is very wide in sensing applications, in the industrial production chain to measure the passage of objects or security alarm system, infrared sensors can be used, the use of light refraction and reflection characteristics to complete the sensing signal, when there is a transmitting end, and receiving end, infrared can also be used for short-range signal transmission, Such as remote controller, infrared transmission interface, etc. However, the general penetration of infrared is not high, active infrared and light reflection principle can also be used in the detection of distance, hit the human skin can calculate the heartbeat and heart rate through microvascular changes.

　　In the "blackbody radiation law", the object temperature above absolute zero (-273.15K) will produce infrared radiation energy; Therefore, the sensing of temperature is often related to infrared rays, and thermal mirrors, thermal tracking systems, and thermal response monitors are the applications of passive infrared sensing. This type of sensor is also often related to our daily life, such as anti-theft systems, fire alarms, ear temperature guns, and so on.

　

　　Ultraviolet light sensor

　　The short wavelength and high frequency of ultraviolet light make the penetration strong, and have certain harm to the human body. When wood, chemical fiber fabric, paper, oil, plastics, and other combustible gases are burned, they will produce ultraviolet light reaction, and the ultraviolet light emitted by sunlight can penetrate quartz, glass, water and air. Combined with the above characteristics, ultraviolet sensors are mostly used in combustion or sun-related sensing applications, such as engine control, flame sensors, solar ultraviolet monitoring, ultraviolet astronomy, light source correction systems, etc., mainly to be measured by motion. The application of active ultraviolet radiation is generally used in medical treatment, and ultraviolet light is often used for sterilization.

　　Ultraviolet light is destructive to the human body. When environmental pollution (ozone layer destruction) causes higher and higher UV value, the probability of skin cancer is also relatively increased. Uv UV sensors will be placed into many sports wearable devices to remind users of the current UV index, which is the main application of UV sensors placed into mobile devices.

　　Image sensor

　　Image sensor is the most complex process in the light sensor, but also the most advanced mainstream products, the sense of radiation light is mostly concentrated in the visible light, with the human eye can recognize the application of imaging, the most well-known example is to replace the traditional film digital camera, relying on the development of image sensors.

　　The image sensor generally needs to be used with a lens to simulate the reaction of the human eye to the RGB red, green and blue primary colors. In order to avoid infrared interference, a layer of infrared filter will be added. With the advancement of CCD and CMOS semiconductor chip production technology, the image sensor can interpret the image quality pixels (Pixel) is very small, and an iPhone App is able to measure the heartbeat by receiving changes in microvessels as long as the finger is pressed in front of the lens and illuminated by the fill light.

　　Today's image sensors can capture images at rest or in motion and analyze the images to make various judgments, such as the camera's autofocus function, the mobile phone APP's smile photo function, and the security system's face recognition.

　

　　Depth sensor

　　It is the most important sensor for virtual reality and gesture control in man-machine interface, which has great potential for future application. The 3D depth sensing scheme is mainly composed of a CMOS image sensor, an algorithm, external components (such as an active light source (infrared IR)) and a main processor. Infrared ray can capture the thermal radiation of the human body, so that the sensing can focus on the master body, not be disturbed by the chaotic background; It can also be used for distance calculation, and with the image sensor to achieve 3D scanning function.

　　In terms of applications, Microsoft's Kinect products are absolutely representative, not only to achieve the dynamic control of the human body in motion sensing games, without wearing any remote control equipment, but also to be applied to many human-computer interaction platforms.

　　Dynamic sensor

　　Dynamic sensor in the measurement of the dynamics of the object, and the 3D depth sensor is different, the dynamic sensor is directly in the actor (people, vehicles) to sense, the so-called "dynamic" of the sensing object includes direction, speed (acceleration sensor), Angle (gyroscope), azimuth (magnetic sensor), height (pressure sensor) several.

　　The way of dynamic sensing usually needs to measure changes in physical quantities (gravity, speed), so it is made of mechanical methods, micro-electromechanical system (MEMS) is an advanced process technology, the traditional mechanical system is tiny to the size of a similar chip, but also today can put dynamic sensors into mobile phones, watches and many other wearable devices important technology.

　　Acceleration sensor

　　Also known as gravity sensor (G-Sensor), accelerometer, used to detect the movement and speed of the object itself; If you want to add direction, one acceleration sensor can sense one axis, two can sense plane movement (X,Y), and three can sense three-dimensional omnidirectional (X,Y,Z) called triaxial acceleration sensors.

　　Many of the current applications of acceleration sensors, in the sense of motion control, such as the game console wii control way as long as the hand remote control. In automobile, the actuating element of the airbag, the auxiliary navigation in the tunnel (acceleration sensor is used to calculate the driving distance because no signal can be received in the tunnel), the wearable device measures the number of steps, distance, calculation of calories, etc., in the future, it can also be used in indoor navigation. In addition, the anti-hand shock function of the camera can also use the sensor to sense the vibration degree. Perform image compensation.

　

　　A pressure sensor

　　Pressure sensors can measure the external pressure formed in water or the atmosphere (also known as air pressure sensors), such as monitoring and management in car engines, tire pressure detection, medical AIDS, aerospace related, etc. In recent years, it has been placed in mobile devices as environmental pressure detection, judging immediate weather changes (also known as weather meters). It can also be used as a vertical altitude positioning system based on changes in air pressure at altitude.

　　Air pressure sensor classification is also a member of the environmental sensor, environmental detection can help us improve the quality of living, mainly air pressure, thermometer, hygrometer, ultraviolet sensor, gas sensor, environmental light sensor several.

　　gyroscope

　　The structure is similar to a gyroscope, which is used to measure the incline and Angle change of the device itself. It was used in the early stage for Angle correction of military and aerospace navigation systems, and dynamic balance scheme of mechanical arms in industrial production. Different from acceleration sensors, gyroscope measurement data is more inclined to slope, rotation and other dynamic information, but has little to do with gravity, linear motion sensing. Gyroscope is more effective in detecting the level change of objects, and cannot have a higher sensing ability for the movement of objects or moving kinetic energy like accelerometers. In contrast, an accelerometer can be useful in detecting the motion state of an object, but it cannot detect small changes in the Angle of an object.

　　At present, most of the applications integrate accelerometers and gyroscopes, so that the dynamic sensing system has the sensing information of direct speed and rotation data at the same time, so that the detection method is more comprehensive and complete. The two are packaged together on a single chip, also known as Inertial Sensing, which is used in the screen rotation control of smartphones and tablets.

　　Magnetic sensor

　　(M-Sensor) uses magnet attraction sensor, which can be divided into induction switch and electronic compass in mobile device applications. Inductive switches such as mobile phones, screen locks on tablets, through the induction of magnets on the protective cover to switch action, if used in industrial production chains can also be used as magnetic induction proximity switches, speed measurement, etc., electronic compass, also known as geomagnetic sensors, use current through semiconductors to sense the magnetic field of nature (Hall effect), Can be used for direction guidance, assist GPS navigation for further confirmation of orientation.

　　At present, most of the geomagnetic sensors are also jointly integrated into the "inertial sensor", so that the direction, speed, various dynamics can be fully recorded and used by the sensor, and can provide high-precision dynamic data, and the future can have a better experience in the somosensory control and dynamic analysis. The development of "indoor navigation" is the common goal of many big factories; In addition to inertial sensors, pressure sensors (barometric sensors) may also be added to measure the current height and floor with subtle changes in air pressure.

　　A sound sensor

　　Sound waves also have different frequencies and amplitudes, which need to be propagated through the medium, and simply distinguish the sound that can be heard by the human ear from the ultrasonic wave that cannot be heard. Sound wave will cause frequency co-shock, and refraction and other characteristics, the way of transmission is caused by resonance with the object in the atmosphere (air, water), which is the principle of the sound sensor, in addition, the sound wave will also produce a refraction image when encountering the object block, so it can also be used as a distance detection.

　　Radio microphone

　　The simplest and most practical sound sensor is actually the microphone we commonly use; The microphone can accurately collect the sound wave of the surrounding environment, and the pursuit of scientific and technological applications is how to convert the sound into usable information or instructions, such as speech recognition function and voice input. However, unlike human beings who can subjectively judge the sound they want to hear, sound sensors are still in the stage of efforts to achieve effective sound source location and sound source separation in sound source analysis.

　　Ultrasonic sensor

　　Ultrasound refers to beyond the sound wave that the human body can hear, using the reflection principle of sound waves, the most common use of ultrasound to measure the distance; Used in service robots, can effectively distance and obstacle avoidance, such as deep water detection, water level measurement, reverse radar, etc., because the refraction of light and sound refraction in the material is slightly different, if the two are used in the detection of the surrounding environment, that is, more accurate environmental detection effect can be achieved.

　　Ultrasound is also often used in medical purposes, such as the principle of pregnant women to see the fetus according to ultrasound, is the reflection characteristics of different density media, resulting in different reflected waves with different tissue density, which is also a ranging application.