Determination of Airborne Water Content Using Photoacoustic Spectroscopy in Laboratory Environment

This laboratory report explores the use of photoacoustic spectroscopy for determining the water content in air, with a focus on practical implementation and demonstration in a laboratory setting. Photoacoustic spectroscopy relies on modulated infrared radiation to induce photonic excitation, accelerating the thermal motion of water molecules in the air. This motion leads to thermal expansion and generates pressure waves that are detected acoustically by a microphone. The experimental setup includes a Helmholtz chamber, a microphone, a speaker, a halogen lamp, and a computer for data acquisition and analysis. To determine the amplitude of the received pressure waves (noise), the IQ demodulation method was employed, ensuring accurate and precise signal interpretation. During the experiment, the humidity of a laboratory room was measured to demonstrate the process. Compared to traditional humidity measurement methods like capacitive or resistive sensors, photoacoustic spectroscopy provides superior sensitivity and molecular specificity, enabling direct analysis without extensive calibration. This makes it particularly suitable for precise humidity measurement and environmental monitoring. This report underscores the potential of this method for applications in sensor development and advanced environmental sensing technologies.