Research And Development Of A COD Detector Based On Sectrophotometric Method

In recent years, the sewage discharge rises continuously due to the developmentof industry and the improvement of people’s living standards, which has posed aserious threat to human health and destroyed the natural ecological system. Chemicaloxygen demand (COD) is one of the important issues of sewage analysis and detection.This thesis presents the study and development of a COD detector.This thesis analyzed the operational principle of COD detection based on thespectrophotometer method and the design scheme of COD detector. According to thesystem requirements, a spectrophotometry COD detector with dual optical structure isdeveloped. Some hardware circuits are designed, including a LED drive circuit, currentintegral circuits and a serial port communication circuit. Then, a measurement andcontrol system based on MSP430FE425single chip microcomputer is built up tosynchronously sample the output current of dual photoelectric detector on the basis ofits internal high precision ADC. The upper limitation of reference sample is fixed toensure that luminous flux constant in each detection. This single-chip microcomputercontrol processing software is also developed to achieve the functions such as serialport communication, LED control, data collection and processing.This thesis investigated the error sources in COD detector from the aspects oftheoretical basis and functional modules, which will provide a guide for the systemdesigning.This present COD detector achieves the required functions of the sewage CODmonitoring system, with the characteristics of real-time, reliable, no secondarypolluting, and provides reliable basis for sewage monitoring. Currently, this CODdetector has been employed in practice.