DESIGN AND IMPLEMENTATION OF MICROCONTROLLER BASED PHOTOACOUSTIC SPECTROMETER AND ITS APPLICATIONS

A compact microcontroller based photoacoustic spectrometer (PAS) has been designed and fabricated. The photoacoustic (PA) cell designed for the present study is of Helmholtz resonator type with a provision to measure the sample behavior as a function of temperature. In this system, an electret microphone is employed to achieve high signal to noise ratio. The microphone compartment is isolated from the sample compartment to avoid the heating effect to the electric microphone which detects the photoacoustic signal. A high-gain low-noise two stage preamplifier, second order bandpass and tunable narrow band-pass filters have been designed with a low noise op-amp LM308 to improve signal quality. C8051F060 microcontroller-based phase sensitive detector has been implemented to measure the amplitude and phase of the signal from the photoacoustic cell. The applications of PAS for phase transition studies on some samples are presented. The designed system is low-cost, very compact and easy to carry the experiments for studying the thermal properties of samples.