Research On Measurement System Of Photoacoustic Spectrum Based On LabVIEW

Photoacoustic spectroscopy (PAS) is a spectroscopic technique whose development is based on photoacoustic effect. This technique has the advantages of high sensitivity, no destruction and wide adaptability etc.. In particular, it offers significant advantages over traditional spectrum techniques in dealing with high scattering, high reflection and opaque material. Thus, It has been widely applied in the fields of gas composition analysis, environment detecting, biomedicine and material science etc..First, this paper reviews the development history of photoacoustic spectral detecting technique and its present situation, then, the RG theory is introduced. Considering the cylinder-shaped photoacoustic chamber as our discussion model, we derive the general expression of photoacoustic signal based on the analysis of its mechanism and have a discussion over some special situations. And then, this paper leads into thoughts of virtual instrument technique and designs a photoacoustic spectral detecting system based on Lab VIEW. Based on the system designing thought, this paper introduces a frame of the system hardware platform and the system software, describes the designing of the pre-amplifier, the main operation interface and several key modules in detail. In the end, the paper makes an introduction of the general debugging of the system:We use laser power energy meter which is flat to the wavelength response to detect power spectrum of the light source, and compare it with photoacoustic spectrum of the carbon sample which is detected by using the system designed in this paper. Moreover, the photoacoustic spectrum of Er2O3 is detected by our system and compared with its standard curve, and the designed system is calibrated using the detected characteristic peaks.The system realizes the high automation for detecting with high efficiency. The system software has a friendly operation interface. In this system, instrument control and parameter setting can be achieved by the computer, data collection, data processing, experimental process dynamic supervisory and result real-time display can also be done automatically with it. The experimental results show the system has high precision and good reliability etc. The innovations of this study are mainly embodied in the works as below:1. A hardware platform of photoacoustic spectral detecting system is built. The platform has a compact structure and is low cost.2. The application software of the detecting system is compiled using LabVIEW. The software adopts the modularized design, especially in the main VI which uses the event driving programming structure, thus improves the computer executing efficiency and is easy to expand function for the system.