Development Of Five-parameter Complex Meter For The Aquaculture’s Water Quality

Our country has a large quantity of aquaculture industry with backward aquaculture technology. With the development of population and increased industrial pollution, it’s urgent to transform the traditional aquaculture way into the modern aquaculture way. It’s difficult to meet the needs of modern aquaculture for the monitoring technology at present. Real-time analysis is of high cost; portable instruments can’t record too much data; the sensors produced in China monitor only one parameter of the water quality, what’s more, its monitoring accuracy is poor; the instruments imported from foreign is expensive. So five-parameter complex meter for the aquaculture’s water quality is developed to solve these problems. Main jobs are as follows:(1) By studying the current monitoring technology of dissolved oxygen, conductivity, pH, water temperature and water level, the Clark DO probe, four terminal conductivity probe and complex pH probe are selected as the sensing part of water quality measurement. The Clark DO probe has long using period with mature technology. Four terminal conductivity probe can deal with the polarization of sensors. Complex pH probe can provide the corresponding membrane voltage. The conditioning circuit is designed so that dissolved oxygen, conductivity, pH, temperature, and water level information can be converted into the voltage signal that the microcontroller can process.(2) To deal with the signal interference of simultaneous acquisition of five-parameter signal, power management module is designed with selecting power supply for each sensing probe. Meanwhile, microcontroller circuit, communication module and alarming module are designed to ensure that, the five-parameter complex meter feasible. A/D conversion process converts the analog signal into digital signal. Software filtering is to filter out the noise of the signal. Data fusion judgment can alarm the water pollution. All of these ways make the five-parameter complex meter smart. (3) To eliminate the bad impact of temperature and other factors on dissolved oxygen, conductivity and other parameters, the module of automatic temperature compensation and calibration, is designed after the studying of the theory and different water quality experiments. The five-parameter complex meter is easy to operate with low cost and high accuracy.(4) In order to know the basic performance index of the five-parameter complex meter, accuracy test, stability test and field practice test are carried out. As a result, the DO measurement range of the five-parameter complex meter is0-15mg/l; the measurement range of conductivity, pH, water temperature and water level are0-70mS/cm,0-60℃,0-14and0-1.5m. Accuracy is less than2.0%, which meets the requirements of monitoring the water quality.