QEPAS Sensor Based on the Tracking of the Photoacoustic Induced Frequency Shift of a Tuning Fork Maintained in Self-Sustained Oscillation by Electrical Excitation

Oscillator frequency shift induced by the photoacoustic force on a closed-loop electrically excited quartz tuning fork is exploited to carry out QEPAS measurement. We report recent improvements of this new method for background-free gas sensing.