Design Of Spectrophotometer Based On Embedded Linux Operating System And Charge-coupled Device

With the growth in demand of analytical instruments which can be used in the areasof rapid detection, market demand provides the opportunity and motivation for thespectrophotometer which has a development trend of portable, intelligent, dedicateddetection and rapid analysis. Standing on the product’s position, this article gives adesign scheme for site rapid detection spectrophotometer, and described in detailabout the specific methods and processes of every component.The paper described the impact on measurement accuracy of the light source andthe sample chamber, designed a Surface array LED light source, gave a detailedsolution to implicit measurement error caused by different refractive index of thesample liquid. According to the line array CCD photoelectric sensor TCD1304,designed a hardware driver circuit, a signal conditioning circuits, and a high-speeddata acquisition circuit controlled by the ARM7microprocessor. In these circuits,Some measures were used to combat interference and reduce the noise, whichensuresed that the12-bit A/D converter achieved to±0.5sample reproducibility andstability in the2MHz sampling rate. Using assembly language, had prepared a highlyefficient ARM7-based acquisition and control software, in the case of continuousacquisition and storage the maximum sampling rate up to5MHz, which made itpossible that using only one ARM7microprocessor could send a high-speed complexCCD control timing as well as the corresponding data acquisition, no external CPLDor FPGA. In addition to these, in order to achieve human-computer interaction andfastly storage or process spectral data, the author had set up the embedded Linuxoperating system on the hardware platform of ARM9. The article described the circuitof ARM9hardware platform as well as the methods and process that how theembedded Linux operating system was transplanted to the hardware platform. In the process of transplantation, the author had prepared the underlying drivers and devicedriver for the peripherals such as SPI, and designed a few common user applicationsoftware.Through the whole debugging,the system’s stability, accuracy in all aspects haveachieved the initial design requirements.