The Research On Temperature,Depth And Salinity Measurement Technology Based On Underwater Sensor Chain

In this thesis,through the research on the development of temperature,depth and salinity measurement technology at home and abroad,the measurement technical index of this system is established,and this thesis also presents a stereoscopic measurement method based on sensor chain.We achieve stereoscopic measurement at the same time by putting the sensor chain into water.The whole measuring system is divided into main board system and secondary board system,and the data collected by the secondary board system is transmitted to the SD card of the main board system for storage.The measuring scheme of this system is determined by studying the measuring principle of temperature,depth and salinity.The thesis choose platinum resistance temperature sensor to measure temperature,and choose the method of pressure sounding to measure water depth,and choose to use practical salinity formula to find salinity.The measurement circuit is designed by analyzing the error source of measurement scheme.The collected information is subjected to analogue-to-digital conversion through the AD7793.And the data are stored in SD card by STM32 microcontroller.We choose the SDIO mode of SD card to transmit data and embedded the FatFS file operating system.We can operate the data on the SD card directly on the computer.This thesis chooses RS-232 serial interface to transmit data,and we define a receive protocol to receive data and apply a loop queue to prevent data loss.The measurement system also uses a clock chip to record the time when data is collected.In order to improve the measurement accuracy,this thesis applies the limiter average filtering to remove the random error.We have carried out the non-linear calibration experiment and used the least squares method to fit the empirical formula.Finally,through the error experiment,we find that after non-linear calibration,the measurement error can be obviously reduced and the measurement accuracy can be improved.And the system meets the requirements of the measurement index of this thesis.