Understand measurement and control technology and instrumentation technology

Measurement and control technology and instrument is a theory and technology that studies the acquisition and processing of information and the control of related elements. “Measurement and control technology and instruments” refers to the means and equipment for information collection, measurement, storage, transmission, processing and control, including measurement technology, control technology, and instruments and systems that implement these technologies.

Measurement and Control Technology
Measurement and control technology and instruments are based on precision machinery, electronic technology, optics, automatic control and computer technology. It mainly studies new principles, methods and processes of various precision testing and control technologies. In recent years, computer technology has played an increasingly important role in the application research of measurement and control technology.
Measurement and control technology is an application technology that is directly applied to production and life, and its application covers various fields of social life such as “the weight of agriculture, sea, land and air, food and clothing”. Instrumentation technology is the “multiplier” of the national economy, the “first officer” of scientific research, the “combat power” in the military, and the “materialized judge” in legal regulations. Computerized testing and control technology and intelligent and precise measurement and control instruments and systems are important symbols and means in the fields of modern industrial and agricultural production, scientific and technological research, management, inspection and monitoring, and are playing an increasingly important role.

Application of Measurement and Control Technology and Instrumentation Technology
Measurement and control technology is an applied technology, which is widely used in various fields of industry, agriculture, transportation, navigation, aviation, military, electric power and civil life. With the development of production technology, measurement and control technology plays a vital role in the control technology from the initial control of a single and its equipment, to the control of the entire process, and even the system, especially in today’s cutting-edge technology in the field of modern science and technology.
In the metallurgical industry, the application of measurement and control technology includes: hot blast furnace control, charging control and blast furnace control in the ironmaking process, pressure control, rolling mill speed control, coil control, etc. in the steel rolling process, and various detection instruments used therein.
In the electric power industry, the application of measurement and control technology includes the combustion control system of the boiler, the automatic monitoring, automatic protection, automatic adjustment and automatic program control system of the steam turbine, and the power input and output control system of the engine.
In the coal industry, the application of measurement and control technology includes: coalbed methane logging instrument in coal mining process, mine air composition detection instrument, mine gas detector, underground safety monitoring system, etc., coke quenching process control and gas recovery control in coal refining process , refining process control, production machinery transmission control, etc.
In the petroleum industry, the application of measurement and control technology includes: magnetic locator, water content meter, pressure gauge and other measuring instruments supporting logging technology in oil production process, power supply system, water supply system, steam supply system, gas supply system, Storage and transportation system and three waste treatment system and the detection instruments for a large number of parameters in the continuous production process.
In the chemical industry, the application of measurement and control technology includes: temperature measurement, flow measurement, liquid level measurement, concentration, acidity, humidity, density, turbidity, calorific value and various mixed gas components. Control instruments that regularly control the controlled parameters, etc.
In the machinery industry, the application of measurement and control technology includes: precision digital control machine tools, automatic production lines, industrial robots, etc.
In the aerospace industry, the application of measurement and control technology includes: the measurement of parameters such as aircraft flight altitude, flight speed, flight state and direction, acceleration, overload, and engine state, aerospace vehicle technology, spacecraft technology, and aerospace measurement and control technology. Wait.
In military equipment, the application of measurement and control technology includes: precision-guided weapons, intelligent ammunition, military automation command system (C4IRS system), outer space military equipment (such as various military reconnaissance, communication, early warning, navigation satellites, etc.).

Formation and Development of Measurement and Control Technology
The historical facts of the development of science and technology The history of human understanding and transformation of nature is also an important part of the history of human civilization. The development of science and technology first depends on the development of measurement technology. Modern natural science begins with measurement in the true sense. Many outstanding scientists dream of being inventors of scientific instruments and founders of measurement methods. The progress of measurement technology directly drives the progress of science and technology.
The first technological revolution
In the 17th and 18th centuries, measurement and control technology was beginning to emerge. Some physicists in Europe began to use the force of current and magnetic field to make simple galvanometers, and use optical lenses to make telescopes, thus laying the foundation for electrical and optical instruments. In the 1760s, the first scientific and technological revolution began in the United Kingdom. Until the 19th century, the first scientific and technological revolution expanded to Europe, America, and Japan. During this period, some simple measuring instruments, such as instruments for measuring length, temperature, pressure, etc., have been used. In life, huge productivity has been created.

The second technological revolution
A series of developments in the field of electromagnetism in the early 19th century triggered the second technological revolution. Because of the invention of the instrument for measuring current, electromagnetism was quickly put on the right track, and one discovery after another grew up. Many inventions in the field of electromagnetism, such as the telegraph, telephone, generator, etc., contributed to the arrival of the electrical age. At the same time, various other instruments for measurement and observation are also emerging, such as the precision first-class theodolite used for elevation measurement before 1891.

The third technological revolution
After World War II, the urgent need for high technology in various countries promoted the transformation of production technology from general mechanization to electrification and automation, and a series of major breakthroughs in scientific theoretical research were made.
During this period, the manufacturing industry represented by electromechanical products began to develop industrially. The characteristics of mass production of products are cyclic operations and flow operations. To make these automatic, it is required to automatically detect the position of the workpiece during the elimination stage of processing and production. , size, shape, posture or performance, etc. To this end, a large number of measurement and control devices are required. On the other hand, the rise of the chemical industry with petroleum as raw material requires a large number of measurement and control instruments. Automated instrumentation began to be standardized, and an automatic control system was formed on demand. At the same time, CNC machine tools and robot technology were also born during this period, in which measurement and control technology and instruments have important applications.
With the development of science and technology, instrumentation has become an indispensable technical tool for measurement, control and automation, starting from simple measurement and observation. In order to meet the needs of various aspects, instrumentation has expanded from traditional application fields to non-traditional application fields such as biomedicine, ecological environment, and bioengineering.
Since the 21st century, a large number of the latest technological achievements, such as nano-scale precision machinery research results, molecular-level modern chemical research results, gene-level biological research results, and high-precision ultra-performance special functional materials research results and global The results of the popularization and application of network technology have come out one after another, which is a fundamental change in the field of instrumentation and promotes the advent of a new era of high-tech and intelligent instruments.

Sensors in measurement and control systems
The general measurement and control system consists of sensors, intermediate converters and display recorders. The sensor detects and converts the measured physical quantity into the measured physical quantity. The intermediate converter analyzes, processes and converts the output of the sensor into a signal that can be accepted by the subsequent instrument, and outputs it to other systems, or is measured by the display recorder. The results are displayed and recorded.
The sensor is the first link of the measurement system. For the control system, if the computer is compared to the brain, then the sensor is equivalent to the five senses, which directly affects the control accuracy of the system.
The sensor is generally composed of sensitive elements, conversion files, and conversion circuits. The measured value is directly felt by the sensitive element, and the change of a certain parameter value of itself has a definite relationship with the change of the measured value, and this parameter is easy to measure and output; then the output of the sensitive element is converted into an electrical parameter by the conversion element; Finally, the conversion circuit amplifies the electrical parameters output by the conversion element and converts them into useful electrical signals that are convenient for display, recording, processing and control.
Current Situation and Development of New Sensors
Sensing technology is one of the fastest developing high-techs in the world today. The new sensor not only pursues high precision, large range, high reliability and low power consumption, but also develops towards integration, miniaturization, digitization and intelligence.

1. Intelligent
The intelligence of the sensor refers to the combination of the functions of conventional sensors and the functions of computers or other components to form an independent assembly, which not only has the functions of information pickup and signal conversion, but also has the ability of data processing, compensation analysis and decision-making.

2. Networking
The networking of the sensor is to enable the sensor to have the function of connecting with the computer network, to realize the long-distance information transmission and processing ability, that is, to realize the “over-the-horizon” measurement of the measurement and control system.

3. Miniaturization
The miniaturization value of the sensor greatly reduces the volume of the sensor under the condition that the function is unchanged or even enhanced. Miniaturization is the requirement of modern precision measurement and control. In principle, the smaller the size of the sensor, the smaller the impact on the measured object and the environment, the less energy consumption, and the easier it is to achieve accurate measurement.

4. Integration
The integration of sensors refers to the integration of the following two directions:
(1) The integration of multiple measurement parameters can measure multiple parameters.
(2) The integration of sensing and subsequent circuits, that is, the integration of sensitive components, conversion components, conversion circuits and even power supplies on the same chip, so that it has high performance.

5. Digitization
The digital value of the sensor is that the information output by the sensor is a digital quantity, which can realize long-distance and high-precision transmission, and can be connected to digital processing equipment such as a computer without intermediate links.
The integration, intelligence, miniaturization, networking and digitization of sensors are not independent, but complementary and interrelated, and there is no clear boundary between them.
Control Technology in Measurement and Control System

Basic Control Theory
1. Classical control theory
Classical control theory includes three parts: linear control theory, sampling control theory, and nonlinear control theory. Classical cybernetics takes Laplace transform and Z transform as mathematical tools, and takes the single-input-single-output linear steady system as the main research object. The differential equation describing the system is transformed into the complex number domain by Laplace transform or Z transform, and the transfer function of the system is obtained. And based on the transfer function, a research method of trajectory and frequency, focusing on analyzing the stability and steady-state accuracy of the feedback control system.

2. Modern Control Theory
Modern control theory is a control theory based on state space method, which is a main component of automatic control theory. In modern control theory, the analysis and design of the control system are mainly carried out by describing the state variables of the system, and the basic method is the time domain method. Modern control theory can deal with a much wider range of control problems than classical control theory, including linear and nonlinear systems, stationary and time-varying systems, single-variable systems and multi-variable systems. The methods and algorithms it adopts are also more suitable for digital computers. Modern control theory also offers the possibility to design and construct optimal control systems with specified performance indicators.

Control System
The control system is composed of control devices (including controllers, actuators and sensors) and controlled objects. The control device can be a person or a machine, which is the difference between automatic control and manual control. For the automatic control system, according to the different control principles, it can be divided into open-loop control system and closed-loop control system; according to the classification of given signals, it can be divided into constant value control system, follow-up control system and program control system.

Virtual instrument technology
Measuring instrument is an important part of the measurement and control system, which is divided into two types: independent instrument and virtual instrument.
The independent instrument collects, processes, and outputs the signal of the instrument in an independent chassis, has an operation panel and various ports, and all functions exist in the form of hardware or firmware, which determines that the independent instrument can only be defined by the manufacturer. , license, which the user cannot change.
The virtual instrument completes the analysis and processing of the signal, the expression and output of the result on the computer, or inserts the data acquisition card on the computer, and removes the three parts of the instrument on the computer, which breaks through the traditional instruments. limitation.

Technical Features of Virtual Instruments
1. Powerful functions, integrating the powerful hardware support of computers, breaking through the limitations of traditional instruments in processing, display and storage. The standard configuration is: high-performance processor, high-resolution display, large-capacity hard disk.
2. Computer software resources realize the softwareization of some machine hardware, save material resources, and enhance the flexibility of the system; through corresponding numerical algorithms, various analysis and processing of test data can be performed directly in real time; through GUI (graphical user interface) interface) technology to truly achieve a friendly interface and human-computer interaction.
3. Given the computer bus and the modular instrument bus, the instrument hardware is modularized and serialized, which greatly reduces the size of the system and facilitates the construction of modular instruments.
The composition of virtual instrument system
Virtual instrument consists of hardware devices and interfaces, device driver software and virtual instrument panel. Among them, the hardware devices and interfaces can be various PC-based built-in function cards, universal interface bus interface cards, serial ports, VXI bus instrument interfaces, etc., or other various programmable external test equipment, The device driver software is a driver program that directly controls various hardware interfaces. The virtual instrument communicates with the real instrument system through the underlying device driver software, and displays the corresponding operation elements of the real instrument panel on the computer screen in the form of a virtual instrument panel. Various controls. The user operates the panel of the virtual instrument with the mouse as real and convenient as operating the real instrument.
The measurement and control technology and instrument major is a traditional and full of development prospects. It is said to be traditional because it has an ancient origin, has experienced hundreds of years of development, and has played an important role in social development. As a traditional major, it involves many disciplines at the same time, which makes it still have a strong vitality.
With the further development of modern measurement and control technology, electronic information technology and computer technology, it has ushered in a new opportunity for innovation and development, which will surely produce more and more critical applications in various fields.