The Design Of Electrode Type Conductance Salinometer With High Precision

Salinity is one of the most important seawater parameters. Its distribution and variation is the one of the most important factors which influence and restrict the other hydrologic factors. Therefore, the accurate measurement of salinity is an important part of Marine hydrographic observations, and it also has many important applications in many fields, such as Aquaculture, Ecological network survey, Climate weather monitoring, Energy exploration, etc. With the rapid development of Marine research, the requirement of the salinity accuracy and automatic measurment degree rise dramatically.This paper first introduced the development of domestic and foreign salinity measuring dynamic, also their research status and significance. It also explains the fundamental of the conductance method for measuring salinity of seawater. Furthermore, this paper analyses the measurement strategies and shortages of the HD-4 type Seawater Salinometer.Considering the salinity accuracy and automation degree problems that lies in the design of HD-4 type Seawater Salinometer, this paper proposes a new kind of design scheme. The new scheme mainly embodies in the following respects:(1) Improve the accuracy of excitation.(2) Use the auto zero point adjustment circuit design to realize the symmetry of the excitation.(3) Improve the accuracy of the standard branch.(4) The design of galvanometer becomes more reasonable.(5) Make special treatment for signal with large noise that influences the specifications of system measurement, which improve the measurement precision and accuracy.After proposing a new design scheme, this paper analyzes the specifications of the new scheme, like accuracy, etc. A conclusion is made that the system can achieve very high resolution and accuracy. The use of the ordinary non-balance electric bridge achieves 1bit expansion, which makes the rate of conductivity reach the accuracy of 7.171*10^-6,meeting the accuracy requirements of 7.171*10^-5.The new scheme design is still based on the SOPC technology, but great improvement has been made on the old system. This paper firstly introduces the conception and development process of the SOPC technology. And then combining with this design scheme, it explains the software and hardware design of the SOPC system in more clear and Concreteness. In this part also introduced the design of the control unit core board (with FPGA as the core). The design does a lot of testing and experiment afer building the whole system according to the design scheme. Firstly it gives the function experiment of the system design, which proofs the extraordinarily reasonable of this design. Then the paper carrys out the performance features experiment, which comes out the conclusion that the accuracy problem of salinity measurement still exists, and it yet gives the reasons for the problem. For analyses of accuracy and experimental data are both needed in the design, the paper gives some methods of data processing used in the design.Finally, the paper gives out the analysis and summariy about the work, and points out that the precision and accuracy has been improved although the result has not reached the demand of the system. The design will do deeper research in the conductance of the seawater to reach the indicators in the next step.