New design principles of electromagnetic flowmeter change traditional application principles

The expected goal of this project is not only to have some basic functions of the traditional electromagnetic flowmeter, but also to make great progress and improvement in intelligence, integration, openness, reliability and computing and processing capabilities. Based on the above analysis and extensive reference to the functions of electromagnetic flow transmitters at home and abroad, we put forward the following requirements for the functions to be realized by electromagnetic flowmeter transmitters, and formulated corresponding design principles to ensure the smooth progress of the project. 2. 1. 1 functional requirements of the System 1. It has the functions of two-way flow measurement and two-way total accumulation: 2. There are three accumulators inside, which can respectively display forward accumulation, reverse accumulation and difference accumulation, and the accumulation quantity can display at least the significant number of lO bit: 3. It has the communication interface of HART standard bus; 4. Two pulse quantity outputs of over-current protection with live isolation and self-recovery functions can output pulses and frequencies, and the unit volume corresponding to each pulse and the frequency of full-scale output can be set; 5, Live isolation and self-recovery function over-current protection alarm signal output, alarm signal definition can be set in the software; 6, live isolation and self-recovery function overcurrent protection 4 ~ 20mh current output; 7, live isolation and self-recovery function over-current protection of one switch input, its function can be set by software; 8. The system comes with a real-time clock, which can record the power-on and power-off time; 9. Low-frequency ternary rectangular wave excitation with adjustable frequency can improve the stability of flow measurement and reduce power consumption; 10, switching type constant current source, the system power consumption is low, the dynamic range of the excitation coil that can be used is large, that is, the internal resistance of the coil is from 0 ~ 70n can meet the requirements: 11. The display unit can be any combination of volume unit or length unit and time unit. The system can automatically and dynamically switch to exponential display to realize the function of large-scale display: 12. Perfect alarm detection capability, such as air traffic control alarm function and excitation fault detection function: 13. It has signal cable shielding drive function, and the sensor and transmitter can be installed separately. 2. 1. 2 System Design Principles 1. Improve system detection accuracy. The detection accuracy is an important index to measure the instrument system. Improving the detection accuracy should be based on hardware circuit design optimization, software processing (Digital filtering, software correction, etc) , Improve the level of excitation technology and anti-interference and other aspects, comprehensive consideration of various factors, the flow detection of interference factors have the necessary technical treatment. 2. Improve system intelligence. The intelligence of the system includes control intelligence and data processing intelligence. When developing this system, the powerful control ability of the microprocessor should be fully utilized, that is, in the process of software control and instrument measurement, a large number of hardware circuits in conventional instruments should be avoided, that is, to achieve 'hardware software' as much as possible '. In addition, the system should have the functions of range selection, excitation mode selection, automatic zero adjustment, etc. Its software should have digital processing capabilities such as digital filtering and nonlinear correction. 3. Improve the openness of the system. System openness includes three parts: hardware circuit openness, software design openness and system communication interface openness. The division of hardware functional modules should be clear, and circuit functional units should be independent of each other. At the same time, the components that make up the circuit unit should have strong universality and good substitution; Readability and expandability should be considered in software design, which is easy for future generations to develop and supports reusability. 4. Improve system reliability. Due to the harsh working environment of the instrument system, in order to ensure the high reliability of the instrument system, mature products should be considered in the selection of devices; In terms of hardware design, it should have the functions of power failure protection and self-diagnosis, and the input and output circuits must have the functions of electrical isolation and overcurrent protection; Anti-interference measures such as fault tolerance, filtering and software traps must be taken in software design. 5. Reduce system cost. Under the condition of meeting the system requirements, in order to obtain a higher performance-price ratio, a simple and practical scheme should be adopted as much as possible, and components with higher cost performance and powerful functions should be selected as much as possible. This can not only reduce the system cost, but also simplify the system structure, reduce the system volume and increase the system reliability. In addition, in addition to hardware costs, development costs and maintenance costs should also be considered when reducing costs. Therefore, mature theories and methods should be selected as far as possible in system development to improve the probability of one-time success in system development, shorten the development cycle and reduce the development cost. 6, improve the system easy to operate and easy maintenance. The system should have a friendly operation interface to reduce the requirements for operators. At the same time, the system should be easy to maintain so that it can be eliminated in time when the system fails.