Design Of Spectrophotometer System

With the development of life sciences,space technology,material science and the other technology,the analysis of the composition of opaque material is becoming more and more important.The heavy metal trace elements which exist in many pharmaceuticals,and foods may lead to carcinogenic and threaten the existence,life and development of our human beings.the analysis of the trace metal elements in Modern science mainly rely on the atomic absorption spectrometry.This method has been used more and more widely because of the three advantages :high sensitivity,strong anti-interference ability and easily to use.We proposed the total design scheme and the integrated hardware and software system of the atomic absorption spectrophotometer based on the main parameters of the performance of the instrument.According to the analysis of the control and functional requirements,we chose the appropriate sensors,components and the corresponding function module unit,and established the hardware control circuit as the core of microprocessor MB90F394 H,the number of lamp elements has been extended to 8,so we don't have to replace the element lamp frequently in the detection of different elements.In order to improve the stability of data in the gas path control system,the integral pulse signals: AAJ and BGJ have been added to the main amplifier circuit.The corresponding circuit in the design includes: A/D circuit,D/A circuit,photoelectric multiplier tube circuit,motor drive circuit,lamp power circuit and peripheral communication interface circuit.The software was wrote by using C++ language,the main program includes display menu subroutine,printer subroutine,A/D conversion subroutine,D/A rotor program,stepper motor driver.The analysis of the elements which interfere the stability and repeatability of the instrument in photomultiplier tube signal processing,the gas flow stability control and graphite furnace atomic system of data acquisition and temperature control had been done,by which we designed the corresponding control system to achieve the purpose of Automated operation and precision measurement in atomic absorption.Finally,we made a summary of the work and look forward to the future research directions.