An Improved Design Of Spectrophotometer With Double Beam

Spectrophotometer is a instrument which produces and utilizes monochromatic light to irradiate the sample and completes the qualitative analysis and quantitative analysis of the sample by measuring the power of the reflected light and trassmitted light. In this thesis a new design scheme is proposed based on the analysis and summary of the basic structure and working principle of the tradional spectrophotometer, in the new design shecme, the grating with a scaning scheme is used in the photometric system, and the filter is used to filter out the stray light, besides these, a AC motor is used to confect the light and switch the optical path.The response range of spectrophotometer discussed in this thesis in the wavelength is 280~2500nm, including the UV,VIS,IR light. The PMT,silicon photovoltaic cells and photodiode is respectively used as the photoelectric converter in different wavelength based on the different sensor's characteristic of spectral response. The weak photoelectric signal is amplified by the muti-stage amplifying circle constructed by the LM358 and ICL7650, and then the analog signal is converted to digital signal by the high-bandwidth 24-bits ADC which is accessed by the system.The system consists of control subsystem and monitoring subsystem. STM32 is the master MCU of the control subsystem, the control subsystem uses TA8435 to control the step motors in order to make the movable parts in a certain position, and employ a part like a photoelectric encoder to synchronize sampling time.Otherwise the monitoring subsystem is a system based on the hardware platform consisted of S3C2440 and the software consisted of Linux and QT, and the subsystem has a characteristic of good man-machine communication experience, besides the control instuction and data are real-time exchanged through the UART between the monitering subsystem and control subsystem. Finally through actual measurement, the precision of the spectrophotometer designed in this thesis is enhanced compared with the similar products.