Design And Research Of New Doppler Current Measurement System

Current measurement is an important link in the field of hydrological monitoring,affecting many aspects of production,life,military and national defense.With the increasing demand for the accuracy of flow current measurement,the Acoustic Doppler Current Profiler(ADCP)has emerged.Its advantage is that it can measure the current of water at different depths at the same time and improve the measurement accuracy.As countries around the world pay more and more attention to hydrology,my country is also gradually developing and improving the related technology of acoustic doppler flow profiler,but there are still gaps compared with the international advanced level,such as poor stability and low measurement accuracy.And the slower computing speed and other issues.In order to solve the above problems,this paper proposes a design scheme of a new type of doppler flow current measurement system.In this subject,guided by the doppler effect and the principle of flow measurement stratification,the measurement method of water current is studied,with the autocorrelation algorithm as the core,the doppler frequency shift calculation formula is deduced,and the blind zone and the side of the measurement process are analyzed.The problem of flap interference,thus confirming the overall research plan.The program includes two parts: hardware circuit design and software program design.The hardware circuit is divided into main control circuit,analog transmitting circuit and receiving circuit.In the main control circuit,ST's latest STM32H743 chip is used as the core processing chip.This chip has rich peripheral resources,fast computing speed and large memory capacity,which improves the overall performance of the system.The transmitting circuit uses the AD9833 programmable signal generation chip to transmit signals of a specific frequency,and an inductance-capacitance matching circuit is designed to ensure that the power of the transmitted signal reaches the expected value.The electronic switch and capacitor filter are used in the receiving circuit for signal orthogonality and filtering,which solves the problem of signal orthogonality and long filtering time in the software,and improves the processing speed of the system.In addition,the system also adds depth and temperature measurement parts for real-time monitoring of water level and temperature changes.The software design part includes the transmission signal output program,data acquisition program,algorithm processing program and data storage program.First,the program drives AD9833 to generate the transmission signal.In the receiving process,the real and imaginary parts of the signal are obtained by the dual ADC synchronous regular sampling mode,use the FFT algorithm to analyze the signal quality,and then use the autocorrelation algorithm to calculate the doppler frequency offset of each layer of the water area and the corresponding flow current value.Finally,the data is stored in the internal FLASH of the microcontroller,and the MODBUS communication protocol is used to realize the communication between the upper computer and the doppler flow rate measurement system,making the whole system more intelligent.After the overall scheme design is completed,multiple sets of comparative experiments and tests are carried out.The experimental results show that,on the basis of certain stability,the system improves the efficiency and accuracy of flow rate measurement,and achieves the expected results and goals of the subject.