Measurement and control technology and apparatus are research information acquisition and processing, and control theory and technology of related elements; It is a high and high technology intensive comprehensive subject which is formed by the interpenetration of electronic, optical, precision machinery, computer, electric power and automatic control technology.
Main process link
The data collection
In signal acquisition, the signal is mainly collected by collecting objects, and then the signal is converted into electrical signals for subsequent processing. Most of the signals sent by the object are collected by sensors, including physical signals (such as temperature: thermocouple/resistance, flow: electromagnetic flowmeter). V cone flowmeter; Vortex street flowmeter, pressure, pressure transmitter, etc.) and chemical signals (such as moisture, odor, etc.) two kinds big, of course also includes not return for some of these two kinds of signals, such as reliability, price, etc. The switching signal (characteristic of digital signal) is mainly based on the instrument with single chip microcomputer, such as the paperless recorder. In addition, image signals are naturally collected by camera devices.
In the process of signal consolidation, it is mainly to transform the collected electrical signals into smooth, filtered, analog-to-digital conversion, which can be converted into a convenient digital signal. The above three types of signal types differ in the content of the collation stage, such as the process of signal amplification, leveling, filtering and analog-to-digital conversion of signals. In the case of the switch volume signal, it can be converted to the required digital signal to be sent to the next processing link after the collection of paperless recorder. For image signal, after acquisition is mainly used to display, if still need to deal with image, display, or a control signals, then must also converting image signal into digital signal, processing, this is a complicated problem.
The signal processing
In the processing phase of the signal, the digital signal is processed in order to display or signal the control signal. We displayed by signals to judge whether the operation of the automation system objects on the normal, if the signal display is not normal, you need for calculation and processing, signal control signal is sent to the object, make the adjustment object to return to normal operation.
In the display and control link, display mainly refers to the digital signal by facilitating we observe in the form of display so that we can judge, control mainly refers to the control signal transmitted to the object is used to process. The above four links constitute the whole measurement process, if including process control, is just form a closed loop, namely the signal from the object, through collection, sorting, processing, and the closed-loop control signal ACTS on the object.
Since the rapid development of computer technology and microelectronic technology has penetrated into the field of measurement and control and instrumentation technology, the field has been constantly updated. Successive intelligent instrument, the bus instrument and virtual instrument, such as instrument of computerization, all without exception, take advantage of software and hardware of the computer, as to strengthen the function of measurement, and improve the technical performance. Since the signal is transformed into digital form, more analysis and processing are done by computers, so it is natural for people to stop focusing on the boundary between the instrument and the computer. In recent years, the speed of new microprocessors has been continuously improved, with advanced technologies such as assembly line, RISC structure and cachE, and greatly improved the computer's numerical processing ability and speed. In terms of data acquisition, the continuous upgrading and updating of data acquisition CARDS, instrument amplifiers, digital signal processing chips and other technologies also effectively speed up the data collection rate and efficiency. Combined with computer technology, it is the main trend of the development of instruments and measurement and control technology. Make a concrete analysis on microcomputer-based instrument, it is not difficult to see, match with corresponding software and hardware of the computer will be able to complete the function of many of the instruments, meters, essentially the equivalent of a multifunctional universal measuring instrument. The function of such a modern instrument is no longer limited by the number of buttons and switches, but rather depends on how much software is installed in it. In this sense, the computer and modern instruments are becoming more and more convergent, and the two have shown global significance. Accordingly, some people put forward the concept of "computer is the instrument"/software is the instrument.
The computer is the backbone of the measurement and control system
The application of microcomputerized instrument, such as bus-type instrument and virtual instrument, makes it easier to form centralized and distributed measurement and control system. But the centralized measurement and control is more and more cannot satisfy the complex, remote (long distance) and the large range of measurement and control task requirements, to form a networked measurement and control system is very necessary, and the continuing escalation of computer hardware and software technology and progress, and gives a measurement and control network is more and more excellent technical conditions. The networked computer operating system, such as Unix, Windows nt, Windows2000 and Netware, has brought convenience to the establishment of networked test system. Standard computer network protocols, such as the OSI RM, open system interconnection reference model on the Internet use TCP/IP protocol, in terms of openness, stability, reliability, all have very big advantage, adopt them is easy to implement and control the system structure of the network. In the development of software, such as Labview and LabWindows/CVI of NI company, VEE of HP company, VB and VC of Microsoft company, all have toolkits for developing network application projects. Software is the key to the development of virtual instrument, such as Labview and LabWindows/CVI is very powerful, not only simple and convenient, makes the development of virtual instrument, and to do on the Internet, the virtual instrument provides reliable, convenient technical support. LabWindows/CVI encapsulates the TCP class library and can develop a network application based on TCP/Ip. Labview's TCP/IP and UDP network VI are able to establish communication with remote applications, and its Internet toolkits add E-mail, FTP, and Web capabilities to the application system; Remote automation VI can also be used to control the distributed VI of other devices. Labview5. In addition, there is a special increase in network function and the ability to develop network applications.
The sharing of resources can be realized by integrating hardware resources such as computers, high-end peripherals and communication lines and software resources such as large databases, procedures, data and files. Secondly, the system redundancy can be improved by means of establishing networked measurement and control system to improve the reliability of the system, so that the system can be extended and changed. The network of computers and workstations as nodes is equivalent to the network of modern instruments. Computers have become the backbone of modern measurement and control systems.
Network technology has become increasingly becoming the key support for the measurement and control technology to meet the actual demand
In today's era, represented by the Internet the rapid development of computer network and related technology is increasingly perfect, break through the limit of time and space and geographical barriers, traditional methods of communication to make a broader range of communication is easy, the Internet has the hardware and software resources are applied in more and more fields, such as e-commerce, online education, remote medical treatment, remote data acquisition and control, remote real-time call high-grade measurement instruments and equipment resources, remote fault diagnosis of equipment, and so on. At the same time, high performance, high reliability, low cost of gateway, router, Repeaters, and network interface chip network interconnection equipment such as continuous improvement, and convenience of Internet, different types of interconnection between the measurement and control network, enterprise network. Use of the existing Internet resources and does not need to set up special topology network, make a measurement and control network, the enterprise internal network and their interconnection with the Internet is very convenient, it is established for measurement and control network widely and used to pave the way. The TCP/IP protocol as a kind of embedded applications, embedded field intelligent instruments (mainly sensor) ROM, make the signal received and sent to the TCP/IP way, so, the measurement and control system in data acquisition, information release, system integration, which is based on enterprise internal network (Intranet), will this network and Intranet and Internet connectivity, acquired is advantageous for the realization of this network and acquired the unification of the information network. In such a form of measurement and control network, the traditional instruments act as the role of independent nodes in the network, information and across the network to any field, real-time, dynamic (including remote) online measurement and control to become a reality, will be such a measure technology compared with the measurement and control, test technology in the past, today, the measurement and control can save a lot of site wiring, enlargement of measurement and control system and regional scope. Make the system expansion and maintenance are the cause of the great convenience, because in the modern measurement task execution and to complete the process, the Internet has played an irreplaceable key role, namely the network really involved in the whole process of the modern measurement and control.