基于激光衍射的液体物性参数测量实验装置研制

Development of experimental device for measuring liquid physical parameters based on laser diffraction

液体毛细波的波矢和振幅反映了液体的表面张力以及粘滞特性,将表面波等效为反射型光栅,其波矢和振幅可通过一束激光的衍射信号测得,从而得到液体的表面张力系数和粘滞系数。基于此原理,文中搭建了光学测量液体表面张力系数和粘滞系数的实验教学装置。装置通过引入频率可调的机械振子以及PID(proportion integral differential)温控模块,实现了变参数测量;对衍射光斑信号使用了边缘探测和类“质心”算法以确定光斑的中心位置和光斑强度,测量了不同温度的水以及不同浓度的酒精的表面张力系数和粘滞系数,验证了实验装置的精确性,表明该装置适合于实验教学推广。

The wave vector and amplitude of capillary wave reflect the surface tension and viscosity characteristics of liquid.The surface wave is equivalent to a reflective grating,its wave vector and amplitude can be measured by the diffraction signal of a laser beam,so as to obtain the surface tension coefficient and viscosity coefficient of liquid.Based on this principle,a set of experimental teaching device for optical measurement of liquid surface tension coefficient and viscosity coefficient is developed.The device realizes variable parameter measurement by introducing mechanical vibrator with adjustable frequency and proportion integral differential(PID) temperature control module.The edge detection and “centroid” like algorithm are used to determine the center position and intensity of the diffraction spot signal.The surface tension coefficient and viscosity coefficient of water at different temperatures and of alcohol at different concentrations are measured.The accuracy of the experimental device is verified,and it is suitable for promotion in experimental teaching.