Design Of Self-contained Measurement System Based On Conductivity Sensor With7Electrodes

Conductivity of the seawater is an important parameter during the marine researchprocess, fast and accurate conductivity measurement has important implications formarine research, marine resources development, etc. Currently there are two maincategories conductivity measurement, they are electrode conductivity sensors andelectromagnetic conductivity sensors. The conductivity sensor with7electrodes getwidespread attention because of its fast response and high accuracy. Through access to alarge number of documents, studies related foreign patents and equipment, with thecharacteristics and actual demand of the conductivity sensor with7electrodes, aself-contained measurement system is designed based on the conductivity sensor with7electrodes in this paper.Firstly, the basic principles and characteristics of the conductivity sensor with7electrodes are described in the paper. Then it is designed to meet the low temperaturedrift, high-precision measurement circuit, based on the physical characteristics of thesensor itself and the high-precision measurement requirements. The system selects anumber of high-precision and low drift devices, the drive signal and acquisition circuitusing the same reference source, to suppress the effects of noise and drift of the systemmeasurement accuracy through rational design of circuits. Using the CPU controlls thedrive frequency. Compared with the traditional way, the drive frequency is more accurateand easy to change. Implementation of high speed sampling the signal by using theanalog to digital converter. Using of mathematical statistics and digital signal processingprocess the data. It can effectively filter out noise and to further improve the precision ofthe system. The system uses real-time clock, high-capacity storage IC chip to save dataand related information. Using the generalized least squares to solve fitting curve duringcalibration of the data.Through calibration and testing, the measurement system achieves the desiredaccuracy. Other aspects of the performance is good. It can satisfy the design requirementsfor self-contained measurement system.