The Research On Key Technology Of Ultrasonic Liquid Level Detection System Based On FPGA

In industrial production,liquid level measurement is widely used in water level monitoring of pipelines,storage volume measurement of storage tanks,and chemical production process control.Accurate liquid level measurement plays an important role in the automatic control of industrial production processes and safe high-quality production,which can effectively prevent the occurrence of dangerous accidents in factories and improve production quality.With the rapid advancement of industrial automation in China,the testing equipment is also developing in the direction of precision,intelligence and miniaturization.Under the comparison of various liquid level measurement methods,this paper selects the ultrasonic detection method with better safety,strong anti-interference ability and non-contact measurement.Ultrasonic testing can be applied to liquid level measurement under special liquid conditions such as corrosive or volatile,and non-contact measurement of liquid level in a closed container.In this paper,based on the non-contact measurement of liquid level,an ultrasonic liquid level detection system based on pulse echo method is designed.The liquid-mode ultrasonic transmission method is adopted,so that the system can be applied not only to the liquid level measurement of the open container,but also to the condition that the container is sealed.Ultrasonic waves with a frequency of 2 MHz were selected by analyzing the application requirements and ultrasonic characteristics.On the basis of design analysis,the whole structure of the system was built,and the hardware circuit design and software design based on FPGA were further completed.In this paper,based on the non-contact measurement of liquid level,an ultrasonic liquid level detection system based on pulse echo method is designed.The liquid-mode ultrasonic transmission method is adopted,so that the system can be applied not only to the liquid level measurement of the open container,but also to the condition that the container is sealed.Ultrasonic waves with a frequency of 2 MHz were selected by analyzing the application requirements and ultrasonic characteristics.On the basis of design analysis,the whole structure of the system was built,and the hardware circuit design and software design based on FPGA were further completed.The hardware circuit design takes FPGA as the core,which mainly includes power supply,ultrasonic transmission circuit,ultrasonic receiving circuit,temperature compensation circuit,communication and display circuit.In the system,ultrasonic transmitting and receiving circuits are designed to generate and receive ultrasonic signals.In order to better realize the analysis of the signal,a high-speed sampling circuit based on FPGA and high-speed AD chip is designed.The flight time of the ultrasonic wave is obtained by analyzing the data of the acquired signal.In addition,the temperature compensation circuit is used to compensate the ultrasonic sound velocity,and the current temperature value is obtained to calculate the sound velocity of the ultrasonic wave.The software design uses the Verilog HDL language to build the internal hardware structure of the FPGA.A modular design approach was adopted to design multiple functional modules for the control functions and data processing and calculations that the FPGA needs to complete.The software design mainly realizes the storage of sampling data,the acquisition of ultrasonic flight time,the temperature acquisition and sound velocity calculation,and the control of each functional chip.The liquid level value obtained through software design analysis is displayed in real time through the digital tube,and transmitted to the upper computer for recording and storage through the serial port protocol.After the board debugging is completed,the water is used as the experimental medium,and the performance index of the designed system is analyzed experimentally,and the feasibility of the liquid level measurement scheme is verified.The experimental results show that the measurement accuracy of the system is high,the standard deviation is small,and the error can be controlled within 1 mm within the measurement range of 60cm.The system works well under dynamic level measurement and can be further applied to online liquid level measurement in industrial production.In addition,it can be seen from the experimental results of the temperature influence that the temperature compensation effect added in the design is better.