Design And Application Of Photothermal Deflection Detecting System Based On Lab VIEW

As an effective method to study the physical and chemical properties of material, the photothermal deflection (PTD) technique, which is developed from the photothermal effect, is a kind of the heat-waves detecting techniques. Because of its advantages, such as the nondestructive detection, high sensitivity and sample-non-pretreatment, the PTD technique has been widely applied to the areas of physics, material sciences and so on, and attracts the deeply attention of domestic and overseas researchers. The traditional photothermal deflection detection system exists the defect that the degree of automation is low, especially in data processing which needs to call other software, such as Matlab and Origin. That will cause the low efficiency in measuring, and can not achieve real-time online processing. LabVIEW is a popular graphical programming language and was took as the development environment of the photothermal deflection detection system in this paper. The research work in terms of hardware and software designs, experiments and applications are as follows:(1) Based on the LabVIEW environment, We designed and developed two sets of the detection system:the photothermal deflection measure thermal diffusivity and the photothermal deflection imaging system, and described the structure and regulation of the experimental system. Automated measurement system was realized in instrument control, data acquisition and data display, and integrated the data processing functions of the photothermal deflection detection technology. The entire experimental procedure can be completed in one program language environment. After several measurements and debugging, the system is running stable, well in man-machine interface, high efficiency measurement, easy to real-time monitoring and control and has good scalability and intuitive.(2) Studied thermal and magnetic properties of amorphous magnetic material though photothermal deflection measurement of thermal diffusivity detection system, and obtained the theoretical analysis. The thermal diffusion rates of two materials which had iron-based and cobalt-based, were determined. Then put the two materials in a magnetic field, compared separately the thermal diffusivity of the two kinds of materials in and out of the magnetic field, plotted the relation curve of a fixed sample’s thermal diffusivity with the angle between the magnetic field and the fixed sample. We also made a preliminary theoretical interpretation of the experimental phenomenon through the analysis of the internal structure of magnetic materials, Meanwhile, the photothermal deflection detection technique is proved to be an effective method to probe the anisotropy structure of material.(3) Using photothermal deflection imaging detection system, We studied the thermal-wave imaging of the subsurface defects of the aluminum samples. By analyzing the photothermal deflection signal amplitude and phase imaging, combine the sample size as well as the scanning initial position, we can accurately determine the location and the scale of defects in material, and give a good reflection of the sub-surface structure of sample. Experimental results correspond well to the theoretical analysis, which prove that the system has a high application value in researching the material thermal properties and sub-surface structure.