The Key Technology Of Side-to-wall Non-invasive Ultrasonic Liquid Level Detection

Liquid level real-time detection in petrochemical,food brewing and power transmission and other general needs and applications,especially for sealed containers of non-intrusive liquid level detection of real-time monitoring and production process is critical.Based on the analysis of the characteristics of common detection method on ultrasonic liquid level,the applicability and essence of the lateral wall-sticking ultrasonic liquid level detection method are analyzed,and on the transmission end insulation porcelain as an example,the key technology of ultrasonic pulse reflection method is studied about single probe.Firstly,the method of liquid level measurement based on the reflection echo of container single interface is studied,and the essence of the method is to determine the liquid level indirectly according to the characteristic impedance value of the medium in the container.In this paper,the impedance test of medium is realized by two schemes,firstly,the relationship between the acoustic pressure of each echo and the dielectric impedance of the interface is analyzed by the first Echo method,and the first echo is most sensitive to the change of dielectric impedance;The second method is to take multiple echo attenuation,extract the interface multiple reflection echo and linear fitting,according to the fitting straight line slope inverse calculation medium ultrasonic impedance.Secondly,the general single interface reflection wave method is more suitable for large container liquid level detection,and like this kind of insulated porcelain sleeve oil filled container,usually only tens of centimeters in diameter,more suitable for the double interface echo method,the liquid level is determined by the presence of the back interface echo.It is easy to distinguish the back echo column from the front interface or the back interface from the transmitting time of the echo signal to the container with large diameter thickness,if there are both the front and back interface echo,which can be concluded that the medium in the container is liquid in the horizontal position of the detection probe;Otherwise for gas.However,when the diameter of the vessel is small and the critical value is reached,the reflection echo signal of the front and back interface will cross and overlap,which is difficult to identify the echo signal,and which is impossible to determine whether there is echo from the back interface and cannot determine the liquid level position.To solve this problem,proposed according to the related interface echo propagation time of a signal processing,filtering window,separate interface echoes,then according to the separation of the signal to valuate the media properties on container corresponding detection point.Thirdly,a new method of liquid level detection-echo envelope area method is proposed based on the concept of energy circle.By calculating the area of the echo signal envelope,generally,under the same test conditions,the solid-gas interface echo envelope is greater than the area of the solid-liquid interface,the solid-gas and solid ?liquid interface was compared,which is the position of the area of the point mutation,namely liquid surface position.Finally,a set of liquid level wireless detection device for oil-filled porcelain sleeve is designed to make ultrasonic liquid level detection more convenient and intelligent.The solution is to solve the problem of leakage oil security in the porcelain sleeve,because of leakage can cause oil level change,the leakage monitoring is converted into liquid level real-time wireless monitoring,and liquid level prediction can be carried out at any time.