光声信号的数字处理

利用数字信号处理技术,可直接应用微机而不用锁定放大器来检测物质的光声信号。本文给出用互功谱技术和多次平均方法所得的一些实验结果。当炭黑和黄色金刚石粉末为试样时,用微机和用锁定放大器所得到的光声信号的相位和幅值都非常吻合。文章还给出了用这数字信号处理技术检测一些薄型不透光试样的热扩散率的实验结果。这些结果与用激光导热仪所测得的结果也良好地相符合。

DIGITAL PROCESSING OF PHOTOACOUSTIC SIGNALS

Using the digital processing technique the photoacoustic (PA) signal of materials can be detected directly with a microcomputer rather than a Lock-in Amplifer. Some experimental results obtained by using cross-spectrum technique and many times average of the sampled signals are given in this paper. For the samples of carbon and yellow diamond powder, both the amplitudes and phases of the PA signals measured by the microcomputer Apple-II are in good agreement with those obtained by the Lock-in Amplifer PAR 5204. Besides, the thermal diffusivities of some opaque thin samples are measured with the above-mentioned method and obtained results are also shown in this paper. Comparing experimental results with those detected by a Laser Thermal Conductivity Detection System for the same samples, we will see a good agreement between them.