| Fluorescence analysis has the advantages of low detection limit for detection samples,strong selectivity to fluorescent substances,low demand for samples to be tested,simple sample preparation method,wide linear range of measurement,etc.In the past few decades,fluorescence analysis has been widely used as a major research method in many fields such as biotechnology,flow cytometry,environmental detection,drug detection,and gene sequencing.Due to the single-machine communication mode,the general-purpose fluorescence spectrophotometer has a large volume and cannot meet the requirements of multi-node detection and miniaturization and portable in environmental online detection applications.Therefore,this paper designs a miniature and compact fluorescence spectrophotometer with aberration-concave grating spectrometry,a stepper motor directly drives the grating to achieve wavelength scanning,and has the networking function based on the MODBUS protocol bus mode.The hardware and software of the control system of the fluorescence spectrophotometer were designed and debugged.The methods of improving the accuracy of wavelength calibration were studied.The performance test and preliminary application of the fluorescence spectrophotometer prototype were carried out.Firstly,the development of molecular fluorescence spectrophotometer is introduced,then the mechanism of fluorescence emission is described,and finally introduces the measurement principle and system framework of such instruments is introduced by this paper.On this basis,the system composition and design framework of the miniaturized networkable fluorescence spectrophotometer are proposed.The system uses 150 W continuous xenon lamp as the light source,and the excitation and emission monochromator adopts the optical structure of the aberrance concave grating.a photomultiplier tube R955 as a detector,a stepping motor directly driving grating wavelength scanning and reducing the size of the instrument.Finally,the design goal of the measurement and control system of the fluorescence spectrophotometer is realized.The main work includes:1.Designed and implemented the fluorescence spectrophotometer circuit and the key hardware of the instrument,including: the main control circuit board,the reference and sample detector circuit board,the light source control module,the excitation and emission monochromator control Grating movement module,reference and sample detector high-voltage modulation module,communication module,etc.,and the electrical connection of the entire instrument.2.A fully functional molecular fluorescence spectrophotometer control and basic application software is desigend and implemented including:firmware drive and fluorescence analysis applications for individual component modules such as direct measurement,fixed wavelength scanning,and dynamics measurement,and for each module The function was tested.3.The method of improving the wavelength accuracy by the wavelength scanning method of directly driving the grating by the stepping motor is studied.The grating linearization algorithm and the Monte Carlo method are used to calibrate the wavelength error,and the satisfactory result of ±0.2 nm accuracy is obtained.The same level of precision as the scanning of the screw structure is achieved.4.The framework structure of MODBUS protocol is studied,and a multi-unit network scheme based on Modbus is proposed.According to the hierarchical structure of the MODBUS protocol,the hardware and software for each layer in the MODBUS protocol are designed and the multi-unit network is finally realized.5.The installation and commissioning of the small fluorescence spectrophotometer prototype was completed and preliminary performance tests were carried out.The wavelength accuracy is ± 0.2nm,and the repeatability is ± 0.1nm.Using the fluorescence spectrophotometer prototype to test the content of chlorophyll a in water samples at a concentration of 10 ～ 100 ug / L still has good linearity,and the deviation of its relative error is within ± 5%. |
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