Electromagnetic flow meter is a measurement of volume flow of conductive media measurement instruments, has high accuracy, good stability and reliability.
In addition to the general electromagnetic flow meter to measure the flow of conductive liquid, it can also measure the liquid-solid two-phase liquid, high viscosity liquids and salts, acid and alkali liquid volume flow can be widely used in cement, chemical, textile, metallurgy, mining, paper, medicine, water, food and beverage, environmental protection and other industrial technology sectors, the performance of their products, quality and reliability of the economic efficiency of enterprises have an important impact.
Embedded Systems (Embedded System) is based on application-centric and computer-based technology, and hardware and software can be laid off to meet the application system functionality, reliability, cost, size, power consumption and other indicators of the stringent requirements of dedicated computer system. It is user-oriented, product-oriented, application-specific systems, compared with the general-purpose computer system has the following characteristics: embedded CPU typically have low power consumption, small size, high integration, low cost, can Many of the general CPU functions done by the board integrated into the chip; embedded system development and application is not easy to create a monopoly in the market; Once embedded system products enter the market, generally have a longer life cycle; embedded hardware and software design must be efficient; embedded systems must have a cross-development tools and environment to be developed.
Parameter measurement instrumentation is to achieve an important part of the process, generally have change, measurement devices and display devices of three parts. The requirements for the instrumentation, software and hardware tailored to achieve a reasonable high level of integration, miniaturization, so not only has the sensor measurement instrumentation, compensation calculation, display function, also has a more powerful information processing, more reasoning, fault diagnosis, self- adaptive learning, intelligent functions. Application of network access technology for embedded systems, but also the instrument to complete remote maintenance, remote control, fault alarm, information publishing and sharing capabilities previously unattainable.
The height of embedded systems technology development, testing and instrumentation technology to bring unprecedented development space and opportunities for intelligent instrumentation, networking and miniaturization paves
The way for the development of instrumentation industry has brought broad prospects.
Generally use traditional electromagnetic flow meter or 16-bit 8-bit microcontroller, the microcontroller performance is weak and peripheral interfaces less complex algorithms can not be completed or the number of parallel tasks; generally used in the display or Segment LED LCD, can display digital , letters, Chinese characters and some rough patterns; commonly used in data storage capacity of the EPROM memory is small, the flow of data storage usually stored in binary, does not have universal; in communication, and generally use the RS 232 or RS 485, the open is not high, a short distance network. To improve the performance and functionality, and some even use a number of electromagnetic flow meter microcontroller way to work together to increase the electromagnetic flowmeter design and implementation complexity. It is necessary to use high-performance 32-bit processor design of electromagnetic flowmeter.
32-bit ARM-based processor and embedded Linux operating system platform for building embedded systems development, and applied to electromagnetic flowmeter design and development, will help to improve the quality of high-end products, electromagnetic flowmeter, to better meet the user needs, but also the level of electromagnetic flowmeter test the development of technology also has important practical significance. As embedded systems design and development complexity and difficulty, this paper constructed a high-performance 32-bit embedded system development platform, can also be applied to other high-end instrumentation design, shorten the development cycle of new product design and enhance their ability to respond to customer needs and product upgrading capability.
An overall design
1.1 ARM processor options
Electromagnetic Flowmeter combines the background, select 32-bit embedded ARM processor. ARM applications processor based on the selection, taking into account the ARM processor price, performance, integration and function, design support and development tools and other factors, and the application of the Ethernet and USB interfaces for functional requirements, choose Atmel's AT91RM9200 chip industry.
1.2 embedded operating system choices
For embedded operating systems typically have a number of assessments that the selection criteria: practicality, the number of resources need to consume (including SDRAM, FLASH MEMORY, etc. ), support for the richness of the software, reliability, and its execution capabilities.
Linux has been ported to many platforms, including ARM, MIPS, SH3, Alpha, X86, PowerPC, etc. , by the tens of thousands of fans developed application software, protocol stacks and a wealth of device drivers; more important is that these drivers Many are in the form of Open Source released, so we all benefit.
1.3 The overall design framework
Program through the selection of electromagnetic flowmeter and the electromagnetic flow meter products and foreign intelligence, integration, network development trends, systems architecture shown in Figure 1. System consists of hardware subsystems and software subsystems.
Electromagnetic Flowmeter hardware subsystems mainly by power supply module, input module, CPU core module, excitation output module, interactive modules, communication interface module and debug interface module. Functional description of each module are as follows:
Power Module: In order to provide the hardware, stable and reliable power supply subsystem.
CPU core modules: the ARM processor, SDRAM, FLASH, and minimum system auxiliary circuits, but also the basic hardware running embedded Linux platform.
Input module: the sensor output voltage or current small signal amplification, filtering, and converted to digital for software processing.
Excitation output module: The D / A converter output frequency three-valued rectangular square wave, and through the power amplifier output to the sensor.
Human-computer interaction modules: the keyboard interface, and TFT LCD interface, the composition of the keyboard and menu system parameters set by the LCD screen real-time display instantaneous flow, cumulative flow and flow curves.
Communication interface module: includes Ethernet interface, USB interface and RS232 interface for data communication and flow transfer functions.
Debug interface module: the JTAG debug interface and debug serial composition DBCOM.