Research And Design Of Conductivity,Temperature And Depth(CTD) Measurement System

Temperature,salinity,and depth are the basic hydrological features of the ocean,the accurate and reliable measurement of which is very important to environmental monitoring,disaster warning and national defense security.With the purpose to develop a miniaturized,low-power consumption and wide-range conductivity-temperaturedepth system(CTD),this thesis carries out research on software and hardware design,sensor calibration,system testing and so forth,and the main work is as follows:(1)A CTD design plan was proposed to fulfill the technical requirements determined by the practical needs of ocean research,which includes underwater measurement module,deck monitoring module and laboratory calibration module.A small-size temperature sensor with high pressure resistance and fast response was designed using NTC thermistor(Negative Temperature Coefficient).It has also introduced the model selection of pressure sensor and the structure design of conductivity sensor.(2)The hardware system design includes circuit design and underwater sealed cabin design.The circuit system consists of excitation circuit,data acquisition circuit,signal transmission and storage circuit.The underwater sealed cabin design includes spatial arrangement design,cabin sealing design and sensor installment design.(3)The software system contains control software,deck monitoring software and calibration software.The control software contains parameter configuration and energy control functions,which can meet the application requirements of a variety of scenarios.The deck monitoring software system has been developed to realize great humanmachine interaction and measurement data visualization.The calibration software has been developed to confirm the best calibration scheme and provide the evaluation of calibration scheme.Meanwhile,a differential compression algorithm designed for the CTD system has been proposed,which improves the storage capacity of the system.(4)The prototype of the CTD system has been developed,and a series of experiments were conducted for performance evaluation,calibration and validation.The accuracy,reliability,repeatability and stability of the measurement were verified.The input/output curve was also obtained in the experiment.The average measurement errors of temperature,pressure,and conductivity are 0.004℃,0.003 MPa,and0.009 m S/cm respectively,which basically meet the design expectations.