Research On High-precision Electromagnetic Flowmeter

Electromagnetic flowmeter is an inductive flowmeter based on Faraday’selectromagnetic induction law. Electromagnetic flowmeters are particularly suitablefor industrial applications and management requirements because they have strongcorrosion resistant ability, high reliability, wide and variable measurement range.With the development of science and technology, electromagnetic flowmeters withhigher accuracy and stability are required. In this paper an intelligentelectromagnetic flowmeter is designed based on a microcontroller with ARM7core,software and hardware anti-interference techniques are developed to improve themeter’s measuring accuracy.The main work of the dissertation includes:(1) The history and status of electromagnetic flowmeter are reviewed, the basictheory and the latest development are introduced in detail.(2) An32bit ARM7core microcontroller was used as the central controller ofthe electromagnetic flowmeter. A compact electromagnetic flowmeter with goodaccuracy and reliability was designed by making full use of the hardware andsoftware resources of the microcontroller.(3) The modular design concept is adopted in the design process of theflowmeter hardware. The designed flowmeter has the advantages of highanti-interference capability and easiness for maintainance. The hardware systemmainly includes the microcontroller system, exciting circuit, signal processing circuit,A/D conversion circuit and empty pipe detection circuit.(4) The design of software system is based on the ADS1.2, and the C languageis adopted as the programming language. The software system design flow chart andpart of the subroutine flow chart are discussed. Haar wavelet filter method is adoptedto overcome the shortcomings of traditional hardware filter circuit, the response timeof the flowmeter can be adjusted online.(5) The prototype electromagnetic flowmeter was calibrated using the standardtank. The result shows that the precision of the prototype is better than±0.3%, andthe performance meets the design requirements.