Research On Measuring And Reconstruction Of The Magnetic Field In Electromagnetic Flowmeter

Electromagnetic flow meter is an important industry measurement instrument,measuring flow based on electric signal from conductive fluid when it passing magnetic field.Therefore,the output character of the meter can be affected by the stability and reliability of its working magnetic field.However,measuring instruments such as gauss meter,magnetometer unable to measure the field's variation and distribution,because of their measurements are single point and steady.The magnetic field in electromagnetic flow meter is always alternating,and its distribution can influence the meter's accuracy seriously.So the available magnetic field measuring instruments cannot meet the measuring requirements of the magnetic field in electromagnetic flow meter.In order to solve the above problems,a magnetic field measurement system based on virtual instrument was developed in this thesis.In this system,magnetic parameters were measured by Hall sensor and NI DAQ system,to monitoring the magnitude and frequency of the magnetic field.Furthermore,the magnetic data were visualized to make its distribution more clear,by using coordinates of measuring points.To improve the reliability of measured results,the Hall Effect was deeply discussed in this thesis,and the elements causing nonlinear error were fund out.As results,output data were fitted according to measured information,and correcting algorithms were realized in LabVIEW.Moreover,a multipoint synchronal measuring Hall probe was developed to test magnetic field speedy with high efficiency.The dynamic magnetic field measuring and visualized method and system were set up after theoretical analysis,experimental testing,software programming,and hardware platform construction.It is demonstrated with experimental results that the developed system was effective in measuring working magnetic field in electromagnetic flow meter,the acquisition data were more acute,and the field waveform and distribution were obtained.The system solved the problem that current instruments cannot acquire comprehensive information of magnetic fields.