A Study On Microscale Dissolved Oxygen Detect Method

Dissolved oxygen(DO) has been widely accepted and used as an important parameter in the area of water resources evaluating. Especially in the field of aquiculture and industry, DO can be a key parameter which has to be measured. In the national standard, iodometric method is used to detect DO. But this method can only measure the DO by mg/L, as a kind of chemical method, this method can not achieve on-line measurement requirements, but also can not be used in the trace detection of DO. The theory of fluorescence quenching can measure the trace DO, but the oxygen sensing film and optical system is very difficult and the cost is very expensive. At the same time, the demand for detection of DO is very extensive. Especially as aquaculture, thermal power, heating boilers, beer fermentation and oilfield water injection and other occasions, the DO content of water requirements are very strict. So a instrument which can measure the microscale of DO quickly and exactly is necessary.A sensor with temperature compensation which can measure content of DO by μg/L is developed in this paper based on electrochemistry. Electrode material, pretreatment method and manufacture method have been researched. A new balance strcture of three electrode is used which not only can short the response time but also can extend the life of sensor. Large number of experiments are did to test the influence of the thickness of oxygen permeable membrane and the duration of the membrane. According to this sensor, a hardware circuit is developed has the function of signal amplification, signal acquisition and result display. MSP430is used as MCU for the sake of energy conservation. At the same time, The accuracy of measurement is promoted though the function of temperature compensation. Multiple point calibration method is used for the sensor, after calibration, compare with the same level inport instrument. Test the performance of self-made insturment and do the actual application in the anaerobic fermentation.Though the experiments, self-made instrument can test the μg/L level of DO and has the advantages of response time, duration and life time. It has high practial value and good application prospect.