The Study Of Detect Cod In Water By The Spectrophotometry

In recent years, the rapid development of industry and the increasing living standards makes sewage discharge increasing, seriously affecting the sustainable development of society and destroy the nature ecological system. Chemical oxygen demand (COD) reflects the degree of water polluted by reducing agents, as one of the comprehensive index to determine the relative contents of organic matter. Therefor the detection of chemical oxygen demand (COD) is very important.This paper analyzes spectrophotometric method determination of the basic principles of chemical oxygen demand (COD) in water and the design scheme of visible spectrophotometer. According to the test characteristics of chemical oxygen demand (COD) developed quasi double beam spectrophotometer is very suitable for chemical oxygen demand (COD) detection. The optical system and photoelectric conversion system have been studied.In the optical system, the high output energy and low stray light is the central idea of the system design, Put forward to taking dissymmetrical Czerny Turner (C-T) structure as the optical structure, taking the plane holographic diffraction blazed grating as the light splitting element. Through the simulation and optimization of optical design software ZEMAX, the system spectrum in the scope of visible light, with a wide spectral broadening, spectral resolution is better than 1nm, optical aberrations of the system control in the range of tolerance. The volume of the structure is about 95mm×90mm×44mm, design meet the high energy output, high resolution, low stray light and miniaturization’s requirement. In The photoelectric conversion system, using the high speed high accuracy logarithmic amplifier Iog114, improves the detecting precision and response speed. Use the COD standard solution calibration Instrument, Compared with HACH-DR6000, that proved the COD detection system’s performance and accuracy are stable and reliable.