Research And Design Of Measure Technology Of The CTD Sensor

With the shortage of land resource and population rapid expansion,every country is keen on the exploitation of ocean.Temperature,salinity and depth as basic parameters to understand ocean,their measures are more important to the exploitation of ocean.A portable tester has been designed to measure the temperature,salinity and depth of shallow sea.The processor of this tester is S3C44B0X and embedded the VxWorks operation system to accomplish the detection of temperature,salinity and depth of seawater.Its advantage is small size,low powers,good expansion and high precision.This paper introduces the current status and development tendency of domestic and foreign CTD,analyses the measure of CTD from theory,and introduces the total design process of hardware circuit in details and deep studies the transplantation of VxWorks operation system and the design of application software.This paper first analyses problems of CTD measurement from theory,such as noise interference of measurement circuit,zero drift,non-linearity of temperature measurement utilizing platinum resistor,polarization effect and capacity effect of electrical conductivity measurement.In the design of hardware circuit,using noise matching principle decreases noise interference;utilizing the technology of DC chopping and dynamic zeroing restrains zero drift;in the measure of conductivity, using AC square waves as driving source which frequency and amplitude can be changed reduces polarization effect;adopting double frequency method eliminates capacity effect.In the design of system software,VxWorks operation system is embedded in the pricessor of S3C44B0X to improve the system reliability,convenient maintenance,modularization design and accomplish portable type finally. Building model of temperature measurement using platinum resistor by BP network eliminates non-linearity.Using iterative arithmetic solves equation in the solution of equivalent resister.In the design of application software,it accomplishes drives of AD conversion,serial port,LCD screen and iterative arithmetic mentioned above.At last,the system is tested via lots of experiments.The result testifies this tester satisfies design requirement.