Brief Discussion on the Development of Automation Instruments

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Brief Discussion on the Development of Automation Instruments [Copy link]

　　Seeing the word "instrument", people will easily think of commonly used test instruments in laboratories such as ammeters, voltmeters, and oscilloscopes. This course is not about discussing these general instruments, but about a special type of instrumentation required in industrial automation, especially in the automation of continuous production processes, called automation instruments. These include detection instruments for measuring process parameters, regulating instruments that issue adjustment commands according to certain adjustment rules based on the deviation of the measured value from the given value, and actuators that control the materials or energy entering and leaving the production device according to the command of the regulating instrument. These instruments measure, control, supervise and protect the production process instead of people, and are indispensable technical tools for realizing the automation of the production process.
　　For beginners of automatic control who have no practical experience, they often think that the job of a control engineer is to draw a control scheme diagram first, and then do it by themselves to design and make certain measurement and control devices to implement the required control algorithm. It is not difficult to imagine that if everyone makes special measurement and control devices for various systems according to their own ideas, their specifications and varieties will be varied and incompatible. For users, their maintenance and spare parts will be unsolvable problems. In order to reduce the variety of instruments and facilitate interchange and maintenance, people standardize the external functions and communication signals of automation instruments, that is, to stipulate several common standardized functional modules, whose internal principles and circuits can be different, but the external functions must be the same. In addition, the interconnection signal standards between them must be unified. These specifications promote the development of automation instruments towards universalization and greatly facilitate users. In this way, for control engineers, the main task is not to make instruments by themselves, but to be familiar with and proficient in the working principles and performance characteristics of various ready-made automation instruments, so as to reasonably select and correctly use them from a large number of serially produced general-purpose automation instruments according to different measurement and control requirements and application environments, and form an economical, reliable and high-performance automatic control system. The main work of automation engineers is "system integration".
　　As a special type of instrument, automation instruments first appeared in the 1940s. At that time, due to the need for automation in industries such as petroleum, chemical, and electric power, multifunctional automation instruments that combined measuring, recording, and regulating instruments appeared. Since then, with the emergence of large industrial enterprises, production has developed in the direction of comprehensive automation and centralized control. People have found that the structure of multifunctional instruments is not flexible enough. It is better to divide the instruments according to their functions and make them into several standard units that can independently complete certain functions. The units are connected with each other by standard communication signals. In this way, the performance of the instrument is easy to improve. In use, you can choose certain units according to your needs, and combine the instruments in a building block style to form control systems of varying complexity. This building block instrument is called a unit combination instrument. Obviously, the practice of decomposing multifunctional instruments into several basic units is beneficial to both the mass production of instrument factories and the selection and maintenance of users. Although in recent years, with the development of automation instruments from analog technology to digital technology, the functional structure of instruments has changed from single function to multi-function again, but this idea of dividing standard units by function is still fully affirmed in the instrument.
　　In addition to the above-mentioned different functional structures, automation instruments can also be divided into electric, pneumatic and other instruments according to the type of energy. Among them, pneumatic instruments appeared earlier than electric instruments, and they are cheap and simple in structure. Especially for inflammable and explosive production sites such as petrochemicals, they have inherent safety and explosion-proof performance, so they have been in an advantageous position for a long time. However, since the 1960s, due to the transistorization and integrated circuitization of electric instruments, the control functions have become increasingly complete. When using low voltage and low current, strict measures can be taken in the circuit and structure to limit the energy entering inflammable and explosive places, so as to ensure that no "dangerous sparks" that are sufficient to cause combustion or explosion will occur at the production site. In this way, a major obstacle that restricts the use of electric instruments in inflammable and explosive places is removed, and the superiority of electrical signals over air pressure signals in transmission and processing can be fully utilized. As we all know, air pressure signals have slow transmission speed, short transmission distance, and inconvenient pipeline installation. In contrast, electrical signal transmission, amplification, conversion, and measurement are much more convenient than air pressure signals, especially electric instruments are easy to use with computers to achieve full automation of the production process. Therefore, electric instruments have achieved an overwhelming advantage.

Jacktang

I understand what automation instrumentation is. Thanks for sharing.