Measurement and control technology paper-technical analysis of intelligent measurement and control instruments
This paper analyzes the characteristics of field bus, puts forward the CAN bus communication scheme of intelligent measurement and control instrument system, and expounds the hardware design and software realization block diagram of general CAN communication interface in intelligent instruments.
Keywords intelligence; Measuring and control instruments
1 Introduction
Fieldbus is one of the hot spots in the field of automation technology. It is called computer local area network in the field of automation. It is a system to realize bidirectional serial multi-node digital communication between microcomputer measurement and control devices. Also known as open, digital, multi-point communication low-level control network. It is a digital, bidirectional transmission and multi-branch communication network connecting intelligent field devices and automation systems. Because it adapts to the development direction of decentralized, networked and intelligent industrial control system, it has advantages in reducing system cables, simplifying system installation, maintenance and management, reducing system investment and operating costs, and improving system performance. It has become a hot spot of global industrial automation technology, which has attracted universal attention all over the world.
Since the late 1980s, several types of fieldbus technology have been developed and widely used in specific fields. These fieldbus technologies have their own characteristics, and some of them have gradually formed their own product series, occupying a considerable market share. Several typical field buses are CAN bus, LonWorks bus and PROFIBUS bus. CAN(ControlArea Network) bus is a kind of field bus designed by BOSCII company in Germany, which is used to realize data communication between internal measurement and executive parts of automobiles. Compared with the general communication bus, the data communication of CAN bus has outstanding reliability, real-time performance and flexibility, which makes its application scope not limited to several automobile industries, but to the fields of machinery industry, process industry and so on, and is more suitable for the interconnection of field-level industrial monitoring equipment. CAN bus specification has become an international standard and is recognized as one of the most promising field buses. Specifically, CAN has the following characteristics: simple structure, only two wires need to be connected to the outside; Flexible communication mode, multi-master mode, regardless of master and slave, can send and receive data in point-to-point, point-to-multipoint and global broadcast mode; Abolish the traditional site coding and replace it with communication block coding; The short frame format is adopted, and the data length of each frame is at most 8 bytes, which can meet the general requirements in the field of industrial control. At the same time, 8 bytes will not occupy the bus for too long, ensuring the real-time communication; Using lossless bus arbitration technology; CRC check is adopted, and corresponding error handling function is provided to ensure the reliability of data communication. CAN node has the function of automatic shutdown, when the node error is serious, it can automatically cut off the connection with the bus without affecting the normal work of the bus.
2 intelligent measurement and control instrument system structure
The system structure of typical intelligent measurement and control instrument based on CAN bus is mainly composed of upper computer and intelligent measurement and control instrument. The main task of the measurement and control instrument is to receive the command of the upper computer, complete the collection of various analog quantities in the industrial field, and realize the control of various production equipment, while the upper computer is responsible for monitoring and managing the whole intelligent measurement and control system. Its tasks include displaying and alarming the status information of CAN nodes, sending commands and control parameters to CAN nodes, receiving data from CAN nodes, displaying curves, storing and printing. These functions can be realized by using the rich resources and powerful functions of modern microcomputers. In addition, through the background processing of the collected data, intelligent functions such as digital filtering PFT transformation can be realized. CAN communication adopts two-wire interface, and the controller of the node to be communicated is connected to CAN bus through CAN driver. Each node has no physical address in CAN communication, but uses software ID to filter the information broadcast on the bus, and determines the priority of information transmission when multiple nodes need to transmit information at the same time.
The communication between the chip and the CAN bus is carried out through the CAN bus transceiver, which is the interface between the CAN controller and the physical bus and provides differential release and reception functions for the bus. In order to realize the communication between PC and CAN bus, it is necessary to use PC's CAN communication card. There are many such cards on the market. You can choose them according to your needs or design them yourself.
Interface design of intelligent measurement and control instrument
CAN bus is a serial data communication protocol. The physical layer and data link layer functions of CAN protocol are integrated in the communication interface of CAN bus to complete the framing of communication data.
SJA 1000 is the follow-up product of PCA82C200 CAN controller of Philips Company. It is compatible with PCA82C200 in software and pins, and has added many new functions and better performance, especially suitable for occasions with high requirements for system optimization, diagnosis and maintenance. The function of SJA 1000 consists of the following parts: interface management logic; The sending buffer can store 1 complete messages (extended or standard); Acceptance filter; Receiving f1f0; CAN core module.
One end of SJA 1000 is connected with a single chip microcomputer, and the other end is connected with a CAN bus. However, in order to improve the driving ability of single chip microcomputer to CAN bus, 82C250 CAN be used as the interface between CAN controller and physical bus, thus providing differential transmission ability to bus and differential reception ability to CAN controller.
If SJA 1000 is used as the CAN controller of flowmeter, it is connected with CPU, and then CAN bus is formed through PCA82C250. This structure is easy to realize the information receiving and sending of CAN network nodes, so as to realize the field control.
CAN communication protocol is mainly completed by CAN controller. SJA 1000 is a highly integrated controller suitable for automobile and general industrial and commercial environment controller area network (CAN). SJA 1000 with simple bus connection can complete all the functions of physical layer and data link layer, and the functions of application layer can be completed by microcontroller. SJA 1000 provides a multi-purpose interface for it.
During the operation of SJA 1000, the control lines (interrupt, reset, chip selection, etc. ) must be configured to establish a hardware connection to communicate with the CAN controller before power-on. Initialization and CAN communication adopt interrupt data sending and receiving subroutine.
If the independent CAN controller receives 1 reset pulses (low level) at pin 17 after power-on, it can enter the reset mode. Before setting the SJA 1000 register, the CAN controller checks whether it has entered the reset mode by reading the reset mode request flag, because the register to be configured can only be written in the reset mode, and it involves the control register CR, the acceptance code register (ACR), the acceptance mask register (AMR), the bus timing register (BTRO and BTR 1) and the output control register (OCR). The clock divider register CAN select BasicCAN or PeliCAN working mode, set CLKOUT pin to enable frequency selection, and set whether to use bypass CAN input comparator and whether to use TX 1 output as special reception interrupt output. The setting of the acceptance code and the acceptance mask register can filter the information and define the acceptance code for the received information; Define an acceptance mask for comparison with the relevant bits of the acceptance code.
The bus timing register defines the bit rate on the bus. The output control register defines the output modes of the output pins TX0 and TX 1 of the CAN bus, and defines whether the configurations of the output pins TX0 and TX 1 are floating, pull-down, pull-up or push-pull, and the polarity. The interrupt register sets the interrupt source that is allowed to be identified.
4 abstract
Many intelligent instruments are connected with PC through CAN interface, and the system runs well. This intelligent instrument system based on field bus has strong anti-interference ability and reliable performance, which is incomparable to traditional instruments in measurement speed, accuracy, automation program and cost performance, and is the development direction of future instruments.
Application analysis of modern electronic measurement and control technology
Modern electronic measurement and control technology is a comprehensive technology based on computer technology, information technology, network technology and electronic technology. With the development of modern society, it is widely used in many fields. This paper mainly discusses the application of modern electronic measurement and control technology and looks forward to the development prospect of this technology.
Keywords: electronic measurement and control; Technology; Characteristics; Development situation
China Library Classification Number: K826 Document Identification Number: A
With the development of modern society and the increasing demand, electronic measurement and control technology has also developed rapidly. This technology is an important part of modern high technology, and it is a comprehensive technology integrating computer technology, information technology, electronic technology, network technology and photoelectric technology. With the upgrading of related technologies, measurement and control technology is constantly moving towards the road of networking, informationization and intelligence. Modern measurement and control technology is to manually record the real-time monitoring data into the computer, and analyze the relevant data with modern computer processing technology to get useful information. With the development of modern measurement and control technology, the speed and accuracy of data information have been greatly improved. With the continuous development of modern society and the improvement of people's living standards, modern measurement and control technology extends to all fields of people's lives, especially in national defense, aerospace, electronics, agriculture and other important fields.
1 introduction of modern electronic measurement and control technology
Modern measurement and control technology is to manually record the real-time monitoring data into the computer, and analyze the relevant data with modern computer processing technology to get useful information. Modern measurement and control technology is mainly automatic control under the guidance of modern measurement and control system, which mainly relies on modern computer processing technology. Composition of modern measurement and control system. Modern measurement and control system mainly consists of five parts: controller, program-controlled equipment and instruments, measurement and control application software, bus and interface, and tested object. Controller is the control and command center of measurement and control system, which mainly refers to computers. Program-controlled equipment and instruments include various program-controlled switches and instruments, storage devices and display devices; Measurement and control software includes driver and application. Bus and interface are the connection channels of various devices and instruments, including connectors and slots. Determine the test object according to different tasks. According to different structures, modern measurement and control systems can be divided into three categories: basic, closed-loop control and standard.
2 characteristics of modern electronic measurement and control technology
With the upgrading of related technologies, the increasingly fierce market competition environment and the diversification and high requirements of people's needs, measurement and control technology is also achieving its own technological breakthrough, and is constantly moving towards the road of networking, digitalization, distribution and intelligence.
2. 1 network
With the expansion of network coverage, the continuous development of computer technology and modern information technology, and the increasingly close relationship between measurement and control technology and modern computer technology, network technology and communication technology, measurement and control technology is gradually moving towards networking. In addition, the application of sensor technology in measurement and control system also makes the use of modern measurement and control technology more convenient. With the continuous updating and development of modern measurement and control technology, its application scope is also deepening, and it is gradually applied to national defense, aerospace, electronics, agriculture and other important fields.
2.2 Digitization
Modern measurement and control technology is to manually record the real-time monitoring data into the computer, and analyze the relevant data with modern computer processing technology to get useful information. It can be seen that the use of modern measurement and control technology is to effectively monitor the subjects in order to obtain useful information. In the society with rapid information development, digital technology is the only way for the development of modern high technology. Digitalization mainly includes communication digitization, signal digitization and multimedia digitization. Multimedia digitization is mainly used for teaching, and communication digitization is mainly to make people's wireless communication more convenient.
2.3 Intelligent
Intelligence is the theme of the development of modern information technology. The most basic mobile phones and computers are intelligent products, and robots are also the result of intelligent development. With the development of modern measurement and control technology, the speed and accuracy of data information have been greatly improved. In order to make the technical development more humane, accurate and convenient, it is necessary to use intelligent instruments in modern measurement and control systems. Based on the development of artificial intelligence and microelectronics technology, intelligent instruments have also developed rapidly, and the application of intelligent instruments in industry will certainly promote the rapid development of industry.
2.4 Distributed
Through the measurement and control equipment distributed in different places, the most suitable instrument can be effectively selected. Distributed measurement and control technology is a modern measurement and control system based on microcomputer technology and network technology and composed of effective distributed devices. The production and control process of distributed instruments is an automatic process integrating testing, control and management, which effectively reduces the cost of measurement and control and improves the efficiency of measurement and control. Distributed means that the five parts of the measurement and control system are organically connected, and the whole system is organically coordinated by using distributed structure to realize the effective operation of the measurement and control system. The distributed characteristics of modern measurement and control system can be safe and reliable, and the fault part will not affect other parts of the system; The development of new interfaces and functions is more convenient, and the system functions have been enhanced; At the same time, the parallel processing mode has the characteristics of high-speed operation; It has a flexible way of use, and can establish multi-module and single-module systems [2]. The distributed management of measurement and control system not only improves the production efficiency, but also effectively saves the cost of manual monitoring. With the development of computer network technology to microcomputer technology, distributed measurement and control technology will be constantly updated and improved.
3 development status of modern electronic measurement and control technology
3. 1 status quo. With the rapid development of advanced science and technology and social economy, the application scope of modern measurement and control technology has been greatly expanded, the development speed is very fast, and the level of measurement and control technology has also been greatly improved. However, there are still many problems, big and small. China's measurement and control technology has not yet entered a high-level development stage, and it still lags behind developed countries in miniaturization, digitalization and intelligence. Therefore, China needs to strengthen the introduction and application of advanced technologies and equipment, learn from foreign advanced technologies and effective development models, strive to keep pace with international technological development, constantly explore and innovate, and strive to narrow the development gap and realize high-level modern measurement and control technology.
3.2 prospects. The development of measurement and control technology is gradually moving towards globalization and networking, which has strengthened the ties among countries in the world more closely and gradually moved closer to the scientific and advanced development trend. The market-oriented development of social economy has greatly promoted the continuous progress of modern measurement and control technology, and then integrated with social development, promoting the development of global science and technology. At present, the rapid development of various industries has also brought the rapid development of measurement and control technology. By analyzing the development of modern measurement and control technology, we can find that openness and standardization are its clear development trend. With the upgrading of related technologies, the increasingly fierce market competition environment and people's diversification and high demand, measurement and control technology is also achieving its own technological breakthrough, and is constantly moving towards the road of networking, digitalization, distribution and intelligence. In the modern society with the rapid development of information technology, the development prospect of modern measurement and control technology is still very broad. The application of modern measurement and control technology, especially in industrial development, has gradually promoted the development and progress of society.
Application of modern electronic measurement and control technology
Modern measurement and control technology extends to all fields of people's lives, especially in national defense, aerospace, electronics, agriculture and other important fields, and plays an important role.
4. 1 agriculture and aerospace
The control and measurement of flying targets in the process of space flight are realized by modern measurement and control technology, which can mainly accomplish the following functions: measuring the physical parameters and motion parameters of spacecraft, measuring the physiological information of astronauts, tracking and measuring spacecraft, controlling and commanding flying targets, monitoring flight status and so on. Agriculture has also integrated the application of measurement and control technology, such as measuring the temperature of grain, giving out high temperature alarm and starting the ventilator to ventilate the granary.
4.2 New sensor technology
New sensor technology is an important aspect of measurement and control technology, which can be applied to all fields of life and production. For example, intelligent sensors are used to monitor the locomotive state of the train and monitor the intracardiac pressure system; Gas miniaturized sensors are mainly used in anti-counterfeiting, national defense, robotics, chemical industry, medicine, transportation and other aspects; The application fields of integrated sensors mainly include: visual measurement, pressure measurement, temperature measurement and so on. The application of digital sensors mainly focuses on environmental temperature measurement and bank monitoring.
4.3 Remote measurement and control
Remote measurement and control is an important part of modern measurement and control technology, which mainly includes wireless communication, telephone network and dedicated line, and can be applied to remote monitoring of power plants, pipelines and oil transportation robots. Modern measurement and control technology can remotely control the automatic plagiarism of gas, water and electricity and diagnose equipment failures.
5 abstract
As a high-tech in the new century, with the continuous development of modern society and the increasing improvement of people's living standards, modern measurement and control technology extends to all fields of people's lives, especially in national defense, aerospace, electronics, agriculture and other important fields. With the diversification and high requirements of competitive environment and people's needs, measurement and control technology is also achieving its own technological breakthrough, and gradually moving towards the road of systematization, networking and intelligence.
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