药品包衣厚度测量系统晶振频率分析及实验研究

Analysis and experimental study of quartz crystal oscillation frequency of drug coating thickness measuring system

为提高药品包衣效果和包衣质量,针对包衣厚度在线监测问题,提出基于石英晶体谐振原理的包衣厚度测量方法。利用石英晶体的压电效应原理分析石英晶体谐振片厚度剪切振动的谐振频率与包衣厚度之间的函数关系,使用等效密度法建立有限元模型并分析石英晶体谐振器在不同膜厚情况下的模态和谐振频率,理论和有限元分析结果均表明晶片的谐振频率随薄膜厚度的增加而降低,且呈近似的线性关系,检测灵敏度约为12 k Hz/μm。使用石英晶体微天平系统进行包衣厚度的测量实验,实测厚度和分析结果具有很好的一致性。研究结果表明基于石英晶体谐振的膜厚测量法可以应用于制药包衣厚度的实时测量。

A method to measure coating thicknesses based on the theory of quartz crystal oscillation was put forward in order to improve the effect and quality of tablet coating and online monitoring. To be specific,the piezoelectric effect theory of quartz crystal was employed to analyze the functional relationship between the resonant frequency of quartz crystal resonator thickness shearing vibration and the coating thickness. Meanwhile,an equivalent density method was used to create a finite element model（FEM） to study the modality and resonant frequency of the resonator under different film thicknesses. The theoretical and FEM outcomes have revealed that the resonant frequency declines with the increase of the film thickness and presents an approximate linear relation,and the detection sensitivity is about 12 k Hz/μm. The findings indicate that the proposed method can be applied to measure pharmaceutical coating thicknesses in real time.