The Integration Design And Study Of Data Processing Algorithm Within Online Dissolved Oxygen Meters

Nowadays, how to detect the water quality has become a key technology as the water pollution control issues have been paid more and more attentions in China. Dissolved Oxygen (DO) is one of the important indicators for water quality; it plays an important role in the governance of water pollution and fish farming. There are three detection methods of DO at home and abroad:iodometry, Clark electrode and fluorescence quenching method.The purpose of this paper is to design a test prototype with stable working performance and good accuracy based on fluorescence quenching; the research consists of two aspects:the designing of hardware circuit and the study of data processing algorithm. The test prototype is composed of the host and probe:the probe aims at the signal acquisition and processing to calculate the DO and temperature in water; the host aims at human-computer interaction to display the DO timely. The work of hardware integration is to accomplish the cooperation of the host and probe and the probability of prototype:the communication between probe and host, designing of the DC power supply and mechanical shell, and the curing of the code. Meanwhile, in order to measure the DO easily, the PLL (phase-locked loop) of detecting fluorescence lifetime has been discussed. The purpose of software progressing is to improve the accuracy and stability of prototype:the functional relationships between fluorescence lifetime, fluorescence quenching coefficient and temperature in water have been found by experimentations to achieve temperature compensation; the standard comparison test has been carried out to adjust the prototype.The digital filtering processing has been taken to process the measurement data to filter out the interference of random pulse and improve the smoothness of measurement data. The final measurement accuracy of this prototype is 0.1mg/L.