Research On Electromagnetic Flow Detection Technology Based On Correlation Detection

With the superior performance,Electromagnetic flowmeter is widely used in the field of flow measurement.However,It is difficult for ordinary electromagnetic flowmeter to obtain flow information when the flow rate of electromagnetic flowmeter is low(less than 0.25m/s)or the external noise is strong.The useful flow signal from the electrodes is easily submerged by noise.Especially,the output flow value of the electromagnetic flowmeter will fluctuate and the measurement stability will be greatly reduced when the measured fluid contains a small amount of solid particles.In recent years,with the continuous development of the relevant detection theory and the expanding application fields,the phase-locked amplification technology based on the relevant detection principle has emerged.The technology can effectively identify the measured signal,and extract the weak signal from the strong noise background by using the known characteristics of the signal.Therefore,this research based on phase-locked amplification technology is of great significance to electromagnetic flow detection technology.Firstly,aiming at the existing problems of electromagnetic flowmeter,the theory of electromagnetic flow measurement technology based on correlation detection principle is studied.In order to improve the signal-to-noise ratio,the principle of weak signal detection using white noise as input noise is analyzed.Then the autocorrelation detection and cross correlation detection technologies are compared and studied.The cross correlation detection of different types of flow signals and reference signals is simulated and analyzed by using MATLAB software.In order to accurately obtain the flow rate information of liquid,the output signal model of electrodes of electromagnetic flowmeter is studied.Secondly,With the oretical research on electromagnetic flow detection technology based on the previous relevant detection principle,the software and hardware design of the electromagnetic flow measurement system with the core of TMS320F28335 digital signal processor is realized.The hardware of the system mainly includes the design of constant current source excitation circuit,flow signal detection and phase-locked amplifier circuit.The acquisition and filtering of the electrode output signal,the flow signal extraction algorithm and the monitoring of the whole system are realized by the system software.In addition,in order to further improve the accuracy of electromagnetic flow detection,based on the previous theory and in-depth study of correlator performance,a differential structure correlation detection method is proposed and implemented.Finally,in order to verify the feasibility and accuracy of the flow measurement system,the electromagnetic flow measurement system is calibrated and tested by the standard meter comparison method,and the differential structure correlation detection test under special circumstances.The experimental results show that the electromagnetic flow measurement system based on correlation detection can not only meet the needs of conventional flow measurement,but also effectively suppress strong background noise,and improve the measurement stability of the system with a small amount of solid particles.Especially the system has unique advantages in the low velocity measurement occasions.It can effectively extract electromagnetic flow signals at low velocity(0.100m/s?0.250m/s)to meet the flow measurement requirements under special circumstances.In order to further improve the detection accuracy and measurement stability of the system,a differential correlation detection method is adopted.The experimental results show that the method has better measurement performance.The research results can be used to provide theoretical support and practical guidance for electromagnetic flowmeter in low flow rate,strong external interference or fluid containing small amount of solid particles.