Abstract :
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.
Keyword :
PAS, photoacoustic spectrometer, phase sensitive detector