Dissolved Oxygen Sensor Design And Measurement System

Dissolved oxygen and pH value are important parameters that measure the quality of water resources,as well as important indicators to judge the self-purification ability of water bodies.It is of great significance for environmental monitoring,industrial and agricultural production to measure the dissolved oxygen content and pH value in water conveniently,accurately and quicklyIn this paper,based on the analysis of the basic principles of electrochemistry,we designed a two-electrode polarographic dissolved oxygen sensor,and introduced the production process of the sensor,including the selection of sensor materials,the development of the two electrodes of the sensor,the configuration of electrolyte and so on.The effects of the surface area of the working electrode and the purity of the auxiliary electrode material on the performance of the sensor,as well as the relationship between the thickness of the oxygen permeable membrane and the response time,were studied through experiments.The stability of the sensor was verified under the conditions of zero oxygen and saturated oxygen respectively.In order to verify the actual performance of the sensor,a hardware processing circuit with signal amplification,acquisition,data storage and other functions is designed.The system uses the low-power STM32F103RCT6 as the main control chip,PT1000 as the temperature measurement element,and the analog-to-digital conversion chip ADS1232 to achieve highprecision measurement.A four-wire platinum resistance temperature measurement circuit is designed to obtain temperature data,and an algorithm is added to provide temperature compensation for the measurement of dissolved oxygen and pH value,which can effectively improve the accuracy of detection.The dissolved oxygen sensor and pH sensor are calibrated by multi-point calibration method,and the data are compared with related high-precision instruments to analyze the measurement accuracy of the system.After debugging and running,the accuracy of the system for temperature measurement is ±0.05℃,and the accuracy of pH measurement is ±0.05.The absolute error of the self-made dissolved oxygen sensor in a zero oxygen environment does not exceed 0.5ug/L,and the absolute error in a saturated oxygen environment does not exceed 0.5mg/L,which satisfies the design index.