| It’s very important to measure the temperature, salinity, depth of seawater for marine science, marine economy, marine environment monitoring. This research subject designs the electrical conductivity sensor based on Van Der Pauw theory, and the temperature sensor based on PT1000, integrates HM20 pressure sensor, completes the system design, hardware and software design, experiment research, develops a stability, sensitivity, inexpensive CTD instrument.This paper introduces the current research progress and background of CTD instrument, and raises the performance requirements of the instrument, according to the demand of ocean observatory project. Designs and manufactures the electrical conductivity sensor based on Van Der Pauw theory, and the electrical conductivity sensor has the feature of great linearity and precise. Designs and manufactures the temperature sensor based on PT1000, and the temperature sensor has the feature of anticorrosion, short response time and small size. Designs the hardware circuit integrated of high-frequency AC exciter, amplifying circuit and signal processing, data collection, communication protocol module based on MODBUS protocol (using RS232 to transfer), and MCU control system. The mechanical structure of CTD instrument aimed on anti-corrosion, well sealed is completed. Designs and codes the MCU program of CTD instrument to automatically control the measurement and data processing. Designs and codes the computer program to communicate with the instrument, save the result and display the monitor curve of temperature, salinity, and depth.Based on this instrument, the parameter of electrical conductivity, temperature and pressure were confirmed by series of experiments. At the same time, this paper tests the precision, resolution, repeatability and reliability of the instrument by series of experiments. The CTD instrument is applied on ocean observatory project, and is proved that the precision and reliability of instrument match the performance requirements. |
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