Automation technology is a comprehensive technology. It has a close relationship with cybernetics, information theory, systems engineering, computer technology, electronics, hydraulic pressure technology, automatic control, etc., and automation is controlled by control theory and computer technology. Technology has the greatest impact. There are a lot of special equipments in the automation technology. Just like the weapons of the people who learn the martial arts, the author makes an inventory of the automated weapons.

A sensor is a common but important device that is a device or device that senses the various quantities being measured and converts them into useful signals on a regular basis. For the sensor, the input can be divided into static and dynamic quantities according to the state of the input. We can get the static characteristics of the sensor based on the relationship between the output and the input under the steady state of each value. The main indicators of the static characteristics of the sensor are linearity, hysteresis, repeatability, sensitivity and accuracy. The dynamic characteristics of the sensor refer to the response characteristics of the input as a function of time. Dynamic characteristics are usually described by models that are automatically controlled, such as transfer functions. Usually, the signal received by the sensor has a weak low-frequency signal, and the external interference can sometimes exceed the measured signal, so eliminating the noise of the serialization becomes a key sensor technology.

A physical sensor is a sensor that detects physical quantities. It is a device that uses certain physical effects to convert the measured physical quantity into a signal in the form of energy that is easy to process. The signal it outputs has a definite relationship with the input signal. The main physical sensors are photoelectric sensors, piezoelectric sensors, piezoresistive sensors, electromagnetic sensors, thermoelectric sensors, and optical fiber sensors. As an example, let's take a look at the more commonly used photoelectric sensors. Such a sensor converts an optical signal into an electrical signal, which directly detects radiation information from an object, and can also convert other physical quantities into an optical signal. The main principle is the photoelectric effect: when light is irradiated onto a substance, the electrical effect on the substance changes, and the electrical effects here include electron emission, conductivity, and potential current. Obviously, devices that can easily produce such effects become the main components of photoelectric sensors, such as photoresistors. In this way, we know that the main working process of the photoelectric sensor is to receive the corresponding light, convert the light energy into electrical energy through a device like a photoresistor, and then obtain the desired output through the amplification and denoising processing. electric signal. The output electrical signal here has a certain relationship with the original optical signal, usually a nearly linear relationship, so that the calculation of the original optical signal is not very complicated. The principles of other physical sensors can be analogized to photoelectric sensors.

The application range of physical sensors is very wide. We only look at the application of physical sensors from the perspective of biomedicine. It is not difficult to speculate that physical sensors have important applications in other aspects.

For example, blood pressure measurement is the most common type of medical measurement. Our usual blood pressure measurements are indirect measurements that measure the blood pressure in the vessel by measuring the relationship between blood flow and pressure measured by the body surface. The sensors required to measure blood pressure usually include an elastic diaphragm that converts the pressure signal into a deformation of the diaphragm and then converts it into a corresponding electrical signal based on the strain or displacement of the diaphragm. At the peak of the electrical signal we can detect the systolic pressure. After passing through the inverter and the peak detector, we can get the diastolic pressure, and the average pressure can be obtained by the integrator.

Let us look at the respiratory measurement technique again. Respiratory measurement is an important basis for clinical diagnosis of lung function and is essential in both surgery and patient monitoring. For example, when using a thermistor sensor for measuring the respiratory rate, the resistance of the sensor is mounted on the outside of the front end of a clip, and the clip is clamped on the nose. When the respiratory airflow flows from the surface of the thermistor, it can pass the heat. A varistor measures the frequency of the breath and the state of the hot gas.

Another example is the most common surface temperature measurement process, which, while seemingly easy, has a complex measurement mechanism. Body surface temperature is determined by various factors such as local blood flow, thermal conductivity of the underlying tissue, and heat dissipation of the epidermis. Therefore, the skin temperature should be measured in consideration of various effects. Thermocouple sensors are used more often in temperature measurement, usually with rod thermocouple sensors and thin film thermocouple sensors. Since the size of the thermocouple is very small, the precision is relatively high, and the micrometer level can be achieved. Therefore, the temperature at a certain point can be measured relatively accurately, and the later analysis and statistics can be used to obtain a more comprehensive analysis result. This is unmatched by traditional mercury thermometers, and it also shows the broad prospects for applying scientific technology to the development of science.

As can be seen from the above introduction, physical sensors have a wide variety of applications only in biomedical applications. The development direction of the sensor is a multi-functional, image-oriented, intelligent sensor. As an important means of data acquisition, sensor measurement is an indispensable device for industrial production and even family life. Physical sensors are the most common sensor family. Flexible use of physical sensors will inevitably create more products and better benefits. .

In recent years, sensors have evolved in a direction that is sensitive, precise, adaptable, compact, and intelligent. In the process, fiber optic sensors, a new member of the sensor family, are favored. Optical fiber has many excellent properties, such as: anti-electromagnetic interference and atomic radiation performance, fine diameter, soft, light weight mechanical properties, insulation, non-inductive electrical properties, water resistance, high temperature resistance, corrosion resistance, etc. It can function in people's ears, such as high-temperature areas, or in areas that are harmful to people (such as nuclear radiation areas), and can also transcend human physiological boundaries and receive sensory senses. Unexpected outside information.

Fiber optic sensors are new technologies that have emerged in recent years and can be used to measure a variety of physical quantities, such as sound field, electric field, pressure, temperature, angular velocity, acceleration, etc., as well as measurement tasks that are difficult to accomplish with existing measurement techniques. In a small space, fiber optic sensors show unique capabilities in environments with strong electromagnetic interference and high voltages. At present, there are more than 70 kinds of optical fiber sensors, which are roughly divided into optical fiber self-sensors and sensors using optical fibers.

The so-called fiber optic sensor itself is the fiber itself that directly receives the outside world. The external measured physical quantity can cause changes in the length, refractive index, and diameter of the measuring arm, so that the light transmitted in the optical fiber changes in amplitude, phase, frequency, polarization, and the like. The light transmitted by the measuring arm interferes (compares) with the reference light of the reference arm, and changes the phase (or amplitude) of the output light, and the measured change can be detected based on the change. The phase of the transmission in the fiber is highly sensitive to external influences, and the interference can be used to detect the physical quantity corresponding to the slight phase change of 10 negative 4th degree radians. By utilizing the winding properties and low loss of the optical fiber, it is possible to form a long optical fiber into a small diameter fiber ring to increase the utilization length and obtain higher sensitivity.

A fiber optic sound sensor is a sensor that utilizes the fiber itself. When the fiber is subjected to a very small external force, microbending occurs, and its light transmission capability changes greatly. Sound is a kind of mechanical wave. Its function on the fiber is to force and bend the fiber. The sound can be obtained by bending. Fiber optic gyro is also a kind of fiber optic self-sensor. Compared with laser gyro, fiber optic gyroscope has high sensitivity, small size and low cost, and can be used in high-performance inertial navigation systems for aircraft, ships and missiles.

Another major category of fiber optic sensors is the use of fiber optic sensors. The structure is roughly as follows: the sensor is located at the end of the fiber, and the fiber is only a transmission line of light, and the measured physical quantity is converted into a change in amplitude, phase or amplitude of the light. In this sensor system, a combination of conventional sensors and fibers. The introduction of fiber optics makes it possible to implement probed telemetry. This fiber-optic transmission sensor has a wide range of applications and is easy to use, but with a slightly lower accuracy than the first type of sensor.

Optical fiber is a late show in the sensor family. It is widely used due to its excellent performance. It is a kind of sensor worthy of attention in production practice.

With its many advantages, fiber-optic sensors have become a rising star in the sensor family, and play a unique role in a variety of different measurements, becoming an indispensable member of the sensor family.

The biomimetic sensor is a new type of sensor that uses a new detection principle. It uses immobilized cells, enzymes or other biologically active substances to interact with the transducer to form a sensor. This kind of sensor is a new type of information technology developed by biomedicine and electronics and engineering in recent years. This sensor is characterized by high performance and long life. Among biomimetic sensors, biosensors are commonly used.

Biomimetic sensors can be classified according to the medium used: enzyme sensors, microbial sensors, organelle sensors, tissue sensors, and the like. In the figure we can see that the bionic sensor and all aspects of biological theory are closely related, which is the direct result of the development of biological theory. Among the bio-simulated sensors, the urea sensor is a recently developed sensor. The application of a biomimetic sensor is described below using a urea sensor as an example.

The urea sensor is mainly composed of a biofilm and its ion channel. The biofilm can sense the effects of external stimuli, and the ion channel can receive the information of the biofilm and amplify and transmit it. When the sensing site in the membrane is affected by an external stimulating substance, the permeability of the membrane changes, causing a large amount of ions to flow into the cell to form a transmission of information. Among them, the membrane protein, which is a component of the biofilm, can produce conformal network changes, change the permeability of the membrane, and transmit and amplify information.

The ion channel of the biofilm is composed of a polymer of amino acids, and a polymer of poly-amino acid (L-glutamic acid, PLG) which is easily synthesized in organic chemistry can be used as a substitute substance, which is better than the chemical stability of the enzyme. PLG is water-soluble and is not suitable for motor modification, but PLG and polymer can synthesize block copolymers to form a sensing film for sensors.

The principle of the ion channel of the biofilm is basically the same as that of the biofilm. After the block copolymer film is fixed on the electrode, if the substance that changes the PLG-protective network is added, the permeability of the film changes, and the current is generated. The change, by the change of current, can be used to detect irritant substances.

The urea sensor has been proved to be a stable biological sensor with good stability. The lower limit of detection is 10 orders of magnitude lower than the power of 3, and it can also detect irritating substances, but it is not suitable for the measurement of the living body.

At present, although many biomimetic sensors have been successfully developed, the stability, reproducibility and mass production of biomimetic sensors are obviously insufficient. Therefore, the biomimetic sensing technology is still in its infancy, so in the future, a new series of biomimetic sensors will be developed. In addition to the existing series, the immobilization technology of bioactive membranes and the solidification of biomimetic sensors deserve further study.

In the near future, olfactory, gustatory, auditory, and tactile biomimetic sensors that mimic biological functions will emerge, possibly surpassing the sensitivity of human facial features, improving the current robot's visual, taste, tactile, and ability to operate on objects. We can see the broad prospects of bionic sensor applications, but these require further development of biotechnology, and we will wait and see this day.

Infrared technology has been developed to the present, and it has been widely used in modern technology, national defense, industry and agriculture. Infrared sensing systems are infrared-based measurement systems that can be divided into five categories according to their function: (1) radiometers for radiation and spectral measurements; and (2) search and tracking systems for searching and tracking infrared targets, Its spatial position and tracking its movement; (3) thermal imaging system, which can produce the distribution image of the entire target infrared radiation; (4) infrared ranging and communication system; (5) hybrid system, refers to the above various types A combination of two or more in a system.

Let us first look at the composition of the infrared system, the main optical system and the auxiliary optical system. On this basis, we will discuss the key components of the infrared in detail. In fact, the working principle of the infrared sensor is not complicated. The working principle of each part of a typical sensor system is as follows;

(1) To be side target. The infrared system can be set according to the infrared radiation characteristics of the target to be side.

(2) Atmospheric attenuation. When the infrared radiation of the target to be tested passes through the earth's atmosphere, the infrared radiation emitted by the infrared source will be attenuated due to the scattering and absorption of gas molecules and various gases and various sol particles.

(3) Optical receiver. It receives part of the infrared radiation from the target and transmits it to the infrared sensor. It is equivalent to a radar antenna and is usually an objective lens.

(4) Radiation modulator. The radiation from the target to be measured is modulated by the radiation, and the target orientation information is provided, and a large-area interference signal can be filtered out. Also known as a reticle and chopper, it has a variety of structures.

(5) Infrared detector. This is the core of the infrared system. It is a sensor that uses infrared radiation to interact with matter to detect infrared radiation. In most cases, it uses the electrical effects exhibited by this interaction. Such detectors can be divided into two types: photon detectors and heat sensitive detectors.

(6) Detector cooler. Since some detectors must be operated at low temperatures, the corresponding system must have refrigeration equipment. After cooling, the device can reduce response time and improve detection sensitivity.

(7) Signal processing system. The detected signals are amplified, filtered, and information is extracted from these signals. This information is then converted into the required format and finally delivered to the control device or display.

(8) Display device. This is the terminal device of the infrared device. Commonly used displays include oscilloscopes, kinescopes, infrared photographic materials, indicating instruments, and recorders.

According to the above process, the infrared system can complete the corresponding physical quantity measurement. The core of the infrared system is an infrared detector. According to the mechanism of detection, it can be divided into two categories: heat detector and photon detector. The heat detector is taken as an example to analyze the principle of the detector.

The heat detector uses the radiant heat effect to cause the temperature of the detector element to rise after receiving the radiant energy, thereby changing the temperature-dependent performance of the detector. Radiation can be detected by detecting a change in one of the properties. In most cases, radiation is detected by thermoelectric changes. When the component receives radiation, causing a physical change in non-electricity, the corresponding change in power can be measured by appropriate transformation.

Infrared sensors have played a huge role in modern production practices, and with the advancement of detection equipment and other parts of the technology, infrared sensors have more performance and better sensitivity.

The magnetic sensor is the oldest sensor, and the compass is one of the earliest applications of magnetic sensors. However, as a modern sensor, in order to facilitate signal processing, a magnetic sensor is required to convert a magnetic signal into an electrical signal output. The earliest application is a magnetoelectric sensor manufactured according to the principle of electromagnetic induction. This magnetoelectric sensor has made outstanding contributions in the field of industrial control, but today it has been replaced by a new magnetic sensor based on high-performance magnetic sensitive materials.

The shape of an electromagnetic sensor

Among the sensors for electromagnetic effects used today, magnetic rotation sensors are an important one. The magnetic rotation sensor is mainly composed of a semiconductor magnetoresistive element, a permanent magnet, a holder, a casing and the like. The typical structure is to mount a pair of magnetoresistive elements on the stimulation of a permanent magnet. The input and output terminals of the components are connected to the fixture, then installed in the metal box, and then sealed with engineering plastic to form a closed structure. This structure has Good reliability. Magnetic rotation sensors have many advantages that semiconductor magnetoresistive elements cannot match. In addition to high sensitivity and large output signal, and a strong range of speed detection, this is due to the development of electronic technology. In addition, the sensor can be used in a wide temperature range, has a long working life, is resistant to dust, water and oil, and is therefore resistant to various environmental conditions and external noise. Therefore, such sensors have received extensive attention in industrial applications.

Magnetic rotation sensors are widely used in factory automation systems because they have satisfactory characteristics and require no maintenance. It is mainly used in the rotation detection of machine tool servo motors, the positioning of robot arms in factory automation, the detection of hydraulic strokes, the position detection of equipment related to factory automation, the detection unit of rotary encoders and various rotating detection units.

Modern magnetic rotation sensors mainly include a four-phase sensor and a single-phase sensor. In the working process, the four-phase differential rotation sensor realizes differential detection by a pair of detecting units, and the other pair realizes differential detection. Thus, the detection capability of the four-phase sensor is four times that of the single element. The two-element single-phase rotation sensor also has its own advantages, that is, compact and reliable, and the output signal is large, can detect low-speed motion, has strong anti-environmental influence and anti-noise ability, and low cost. Therefore, single-phase sensors will also have a good market.

Magnetic rotation sensors also have great application potential in household appliances. In the reversing mechanism of the cassette recorder, a magnetoresistive element can be used to detect the end point of the tape. Most of the home video recorders have variable speed and high speed playback functions. This can also be used to detect and control the spindle speed with a magnetic rotation sensor to achieve high picture quality. The forward and reverse rotation and high and low speed rotation of the motor in the washing machine can be detected and controlled by the servo rotation sensor.

Electromagnetic proximity switch

This switch senses metal objects entering their inspection area and controls the opening or closing of their internal circuits. The switch itself generates a magnetic field that causes a change in the magnetic field when a metal object enters the magnetic field. This change can be turned into an electrical signal through the internal circuitry of the switch.

Electromagnetic sensors are a high-tech application with a wide range of applications. Domestic and foreign countries have invested in certain scientific research forces. The application of such sensors is penetrating into various fields of national economy, national defense construction and people's daily life, along with information. The status and role of society will be more prominent.

Modern electric measurement technology is becoming more and more mature. It has been widely used in the measurement of electrical quantity and non-electric quantity because of its high precision and convenient automatic real-time processing by microcomputer connection. However, the electrical measurement method is susceptible to interference. In the case of AC measurement, the frequency response is not wide enough and there are certain requirements on the withstand voltage and insulation. In the rapid development of laser technology, the above problems have been solved.

Magneto-optical effect sensors are high-performance sensors developed using laser technology. Laser is another new technology that developed rapidly in the early 1960s. Its appearance marks a new stage in which people master and use light waves. Due to the low monochromaticity of ordinary light sources in the past, many important applications have been limited, and the emergence of lasers has made radio technology and optical technology soar, interpenetrate and complement each other. Nowadays, many sensors have been made using lasers, which solve many technical problems that could not be solved before, making it suitable for dangerous and flammable places such as coal, oil and natural gas storage.

For example, an optical fiber sensor made of laser can measure the parameters of crude oil injection and cracking of large oil cans. In the actual measurement location, it is not necessary to supply power, which is especially suitable for the petrochemical equipment group where the safety explosion-proof measures are very strict. It can also be used to realize the optical telemetry technology in some aspects of large steel plants.

The principle of the magneto-optical effect sensor is mainly to realize the function of the sensor by utilizing the polarization state of the light. When a beam of polarized light passes through the medium, if there is an external magnetic field in the direction of beam propagation, the light will rotate through an angle of polarization, which is the magneto-optical effect. That is, the applied magnetic field can be measured by the angle of rotation. Under a specific test device, the angle of deflection is proportional to the intensity of the output. By illuminating the laser diode LD with output light, a digitized light intensity can be obtained for measuring a specific physical quantity.

Magneto-optical effect sensor

Since the end of the 1960s, RC Lecraw has raised the attention of the research report on magneto-optical effects. Japan, the Soviet Union and other countries have carried out research, and there are also scholars in the country to explore. The magneto-optical effect sensor has excellent electrical insulation performance and anti-interference, wide frequency response, fast response, safe explosion-proof and so on. Therefore, it has unique effects on the measurement of electromagnetic parameters in special occasions, especially in high-voltage and high-current in power systems. The measurement aspect shows its potential advantages. At the same time, automatic real-time measurement of the welding machine and the robot control system can also be realized by developing the software and hardware of the processing system. In the use of magneto-optical effect sensors, the most important thing is to choose magneto-optical media and lasers. Different devices have different capabilities in terms of sensitivity and working range. With the advent of high-performance lasers and new types of magneto-optical media in recent decades, magneto-optical effect sensors have become more and more powerful and have become more widely used.

The magneto-optical effect sensor is a special-purpose sensor that can perform its functions in a specific environment and is also a very important industrial sensor.

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