Design And Development Of Expendable Sound Velocity Profiler (XSV) Measurement Circuit

Seawater sound velocity is the basis for other marine instrumental measurements,therefore,obtaining accurate seawater sound velocity is the core of ocean exploration.There are many types of products for seawater sound velocity measurement,but the Expendable Sound Velocity has the advantages of low cost,convenient testing and real-time access,so the equipment is widely used in scientific research,marine exploration,marine military and other fields.At present,the development of foreign Expendable Sound Velocity is relatively mature,but the domestic product is still in a blank state,so it is very necessary to develop a domestic Expendable Sound Velocity.The Expendable Sound Velocity(XSV)mainly includes the underwater sound speed measurement system jointly controlled by the single chip STM32L4 and CPLD,the enameled wire and the data receiving system controlled by the single chip STM32F4.The underwater sound velocity measurement system uses the pulse ring method to measure the seawater sound velocity.In the hardware circuit,the modular design is used to design the signal transmission drive circuit,the signal frequency selection amplifier circuit,the amplification circuit,the envelope detection circuit,the threshold comparison circuit,and the pressure.Measurement circuit,underwater driving circuit,data storage circuit;In terms system control,the CPLD completes the sound velocity excitation signal transmission,timing control,counting of frequencies to be measured,data transmission and equal precision frequency measurement algorithm;the single chip microcomputer STM32L4 complete the sound velocity measurement switch control,use the SPI mode to read sound velocity data,collect pressure(depth)data,store the fitting coefficient,write 2DPSK modulation algorithm,convert the data into 2DPSK signal and transmit it to the enameled wire through the underwater driving circuit.The enameled wire is used as the data transmission medium.In the data transmission process,the enameled wire is equivalent to a plurality of low-pass filters connected in series to filter the 2DPSK signal.In the water data receiving system,the water receiving circuit is designed,and the signal acquisition is completed by the single chip STM32F4.The 2DPSK demodulation algorithm is programmed to realize the demodulation of the 2DPSK signal.The serial communication circuit is designed to output the collected sound velocity and depth data in real time,and draw the ocean sound velocity distribution profile.Finally,hardware debugging and product testing were carried out on the Expendable Sound Velocity meter,and a large number of experiments and test work were carried out.The polynomial fitting process was carried out on the measured seawater sound velocity data,and the data error analysis was carried out to obtain the sound velocity measurement accuracy of the Expendable Sound Velocity.This design meets the project indicator requirements and verifies the correctness of the solution.