At present, in the field of industrial production, the application of automated control systems in large and medium-sized enterprises has gradually become common.
At present, in the field of industrial production, the application of automated control systems in large and medium-sized enterprises has gradually become common. In the automated control system, various electromagnetic flowmeters and other flow, liquid level, concentration, and temperature instruments can be used to control production. Various indicators and parameters in the process are monitored and controlled in real time to meet the requirements of automated production. Therefore, the stability and reliability of the instrument are key factors related to the normal operation of the entire automation system. If interference or failure occurs in the instrument, it will lead to the failure of the monitoring and automation control system. The author has worked in the industrial automation control industry for many years. Based on many years of practical experience, this article briefly introduces the common characteristics of various types of automation instruments such as electromagnetic flowmeters, and analyzes the various performances of these instruments when they are interfered with. This article takes an automated control system as an example to summarize the practice of automatic control instruments in preventing interference, and proposes corresponding anti-interference measures for reference by relevant personnel in the industry. In recent years, with the continuous improvement of social production automation level, automated control instruments have been gradually applied to the production process. The application of various instruments provides quantitative indicators for staff to understand the operating status of machinery, pressure conditions, and production environment conditions. However, affected by factors such as electromagnetic waves, mechanical operation, operating temperature and humidity, the automatic control instrument system is easily disturbed, which in turn leads to errors in the displayed values of the instrument. It can be seen that in order to further improve production efficiency and safety, it is necessary to study the anti-interference problem of instruments.
1 Common types of automatic control instruments
1.1 Electromagnetic flowmeter Electromagnetic flowmeter is the main instrument type used in chemical production. It consists of a magnetic circuit system, measuring conduit, electrode, converter and other parts. Among them, the magnetic circuit system is the core part of the instrument. The purpose of this system is to generate a magnetic field. By measuring the flow of conductive media in the conduit, the operation of the power system during the production process is observed. To determine whether the performance of the power system can be performed stably. The common interference during the use of electromagnetic flowmeters is mainly electromagnetic interference [1]. In addition, the quality of internal components and wiring conditions will also affect its performance. It can be seen that in order to improve production efficiency and safety, actively preventing the above interference is key. 1.2 Liquid level gauge Liquid level gauge is a type of level instrument, including input type, magnetic float type and so on. Applying it to the chemical production industry can effectively determine the location of liquids. As the position of the liquid changes, the float changes accordingly. At this time, the height of the liquid level can be clearly reflected in the instrument. The magnetic float instrument consists of two parts: a liquid level sensor and a signal converter. When the position of the liquid changes, the magnetic position sensor can subsequently measure its position [2]. And transmit the measured information to the signal converter. After the signal converter receives the signal, it can immediately convert it into a displayable signal and output it, finally completing the process of liquid level monitoring. 1.3 Concentration meters According to different measurement principles, concentration meters can be divided into rotary type, moving knife type, fixed knife type, electric type, etc. The function of this instrument is mainly toThe concentration of a substance in a liquid is measured. HGY2058 acid-base salt concentration meter is a type of online monitoring concentration meter. The instrument can be connected to a sensor to detect the concentration of highly corrosive media without coming into contact with the measured medium. Applying this instrument to the chemical production industry can enable staff to grasp various concentration indicators in a timely manner. Then, through the adjustment of indicators, the quality and safety of chemical production can be improved.
2 Interference performance of automatic control instrument systems
2.1 Electromagnetic interference Electromagnetic interference is a common type of interference for electromagnetic flowmeters, liquid level meters, and concentration meters. In view of the functions of the above instruments, they all need to be performed in an electromagnetic environment. Therefore, once electromagnetic interference occurs, the accuracy of instrument measurement indicators will inevitably be affected [3]. During the operation of the instrument, electricity and magnetism can interfere with the instrument through the circuit and magnetic circuit. If there is a strong magnetic field in the environment around the operation of the instrument, obvious interference voltage will often be visible when measuring the circuit and wires of the instrument. The above phenomenon shows that the electromagnetic environment around the instrument has affected the reliability of its operation and the accuracy of its parameter display. It needs to be resolved immediately to prevent increased risks in chemical production. 2.2 Mechanical interference In the process of chemical production, inaccurate instrument parameters caused by mechanical interference often occur. The causes of mechanical interference problems are related to the vibration, knocking, impact and other work performed by construction workers. In the automatic control instrument system, each component has the highest precision and sensitivity. After being impacted by external forces, it is very easy to cause deformation, dislocation, and changes in connecting lines. The pointers of some instruments will also change. It can be seen that it is key to improve the stability and safety of instrument operation, and to adopt corresponding systems to monitor corresponding indicators on the basis of strictly controlling the mechanical operating status. 2.3 Environmental interference During the operation of the instrument, changes in temperature and humidity will cause interference to it. Electromagnetic flowmeters, liquid level meters and concentration meters in the chemical production industry contain a large number of semiconductors. The main function of semiconductors is to conduct electricity. Its electrical conductivity is significantly related to changes in light. Therefore, if the change in light is too large, the conductive performance and operating status of the instrument will inevitably be affected. In addition, leakage and expansion phenomena caused by excessive ambient humidity, as well as changes in circuit device parameters caused by excessive ambient temperature, will also cause interference to the automatic control instrument system.
3 Anti-interference strategy of automatic instrumentation system
3.1 Structure of ControlLogix system Applying ControlLogix system to automatic instrumentation system can effectively improve the anti-interference performance of the instrument. The system is mainly composed of Logix5560 processor, ControlLogix I/O module, ControlLogix backplane, and power supply. It includes three layers: equipment layer, control layer and information layer. Among them, the function of the equipment layer lies in the use of "electromagnetic flowmeter", "liquid level meter" and "concentration meter"Deadlines, and their failure situations are managed. The function of the control layer is to specifically realize the optimal control of the instrument operation. The function of the information layer is to extract the information generated by the system and determine whether the operation of the instrument is at risk of being interfered with. 3.2 Anti-interference strategy (1) Filtering scheme ControlLogix system can be connected to the filter to achieve the purpose of reducing interference in the automatic control instrument system. During the operation of the filter, the interference coupled to the circuit through the wire can be suppressed in real time. When the frequency of signals and noise around the operating environment of the instrument is too high. The ControlLogix system can immediately collect the above information, store it in a database, and analyze the information. The information after the analysis is completed will be transmitted to the filter. At this time, the filter will be immediately connected to the transmission channel to exert its filtering effect. Finally, the purpose of reducing attenuation noise and improving signal-to-noise ratio is achieved. This solves the interference problems faced by various instruments during operation and improves the accuracy of instrument parameters. (2) Control power supply In the chemical production process, it is difficult to effectively avoid interference of various instruments due to vibration problems. After the instrument is interfered, controlling the interference within a certain range is the key to ensuring that the production process can continue. During the power supply configuration process of the automatic control instrument system, the abnormality of different power supplies automatically cuts off the circuits and can be connected to each other. When an abnormality occurs in an instrument, the instrument cannot be isolated, and interference will occur. In order to solve the above problems, the ControlLogix system can be applied to the interference suppression process. On this basis, configure the system redundantly. When a mechanical interference occurs to an instrument, the ControlLogix system will immediately exert its redundant function, cut off and isolate the instrument to avoid expanding the scope of the interference. (3) Optimize the environment. The ControlLogix system can monitor the operating environment of electromagnetic flowmeters and other instruments. When abnormalities in the temperature, humidity and light environment are found, it will immediately give an early warning and remind relevant personnel to deal with it. For example: An electromagnetic flowmeter malfunction occurred in this chemical company. On the day of the incident, the ambient temperature was relatively high. In addition, the air humidity is high, so the parameters of the electromagnetic flowmeter are abnormal. After the incident, the staff received the early warning information from the ControlLogix system in time and adjusted the ambient temperature in a timely manner, thus solving the interference problem. This shows that optimizing the environment is more important. 3.3 Anti-interference effect This manufacturer introduced the ControlLogix system in early 2009 and applied it to the automation system. Through the observation of the operation of the respective control instruments before and after the system is applied, it is found that: 1) Before the system is applied: the electromagnetic flowmeter, liquid level meter, and concentration meter malfunction due to interference more than 20 times per year, and the cost of repairing the instruments is The cost is 170,000 yuan. 2) After the application of the system: the average number of malfunctions caused by electromagnetic flowmeter, liquid level meter and concentration meter per year due to interference are 2 times, 0 times and 1 time respectively. After the interference occurred, the staff at CUnder the early warning instructions of the controlLogix system, the source of interference was immediately eliminated and the interference maintenance cost was reduced to 39,000 yuan. By comparison, it was found that the application of the ControlLogix system achieved good results.
4 Conclusion In summary, the research on anti-interference strategies for automatic control instrument systems provides important reference materials for the popularization and application of ControlLogix systems and the improvement of instrument operation stability in various industries in my country. And to a certain extent, it reduces electromagnetic interference, enhances mechanical performance, and optimizes the operating environment of the instrument. In the future, various fields in our country should consider automatic control instruments and their common interference types, and achieve the purpose of anti-interference by applying filtering technology, controlling power supply, and optimizing the environment, so that the performance of the instruments can be further enhanced.
Hangzhou Economic Development Area，Hangzhou 310018，China
