Development Of Seawater Chemical Oxygen Demand Analyzer By Ozonation Base On LabVIEW

Ocean is China's important resources for the sustainable development of economy and society. The quality of the marine ecological environment is closely related to human survival, production, life and health. The chemical oxygen demand (COD) is an important index for monitoring the propagating of ocean organic substance, and is also an important parameter for monitoring seawater quality. It is essential to detect and control the seawater COD in time for understanding the marine pollution of organic substance.Usually the COD of seawater is relatively low, so a higher sensitivity is required for the measuring instrument. The influence of Cl" on the analyzer is also needed to be overcome.In this dissertation, the ozonaion chemiluminescence principle is used to determine the seawater COD, a COD analyzer based on LabVIEW is successfully developed finally. Using high-performance modular hardware and combining with efficient and flexible software, LabVIEW is convenient for signal acquisition and processing, which greatly shorten the development cycle of COD analyzer. This COD analyzer has many features such as in-situ, real-time, rapid, no secondary pollution.This dissertation describes the COD analyzer's working principle, hardware, software and experimental results. The COD analyzer takes ozone with stable density, which is provided by the electrolytic ozone generator, as the oxidizer, and uses chemical luminescence as testing method to obtain the seawater COD value by processing the measured optical signals. The kernel of instrument hardware is PC/104 computer. The host computer software controls the sampling system, ozone generator, data acquisition and communication. PM511P data acquisition board is used to obtain and process temperature and light signals.LabVIEW, a graphical programming software, is used to program. The core idea of signal acquisition is introduced in detail. Multithreading technology is used to improve software performance.Automatic measuring module, manual measuring module, and data communication module of the COD analyzer are also introduced.The accuracy of this measuring method is examined by in-situ contrast experiments.The measuring results from both proposed method and national standard method are in good linear relationship, showing that this method is correct, reliable and sensitive, also can meet the needs of seawater COD measurement.