New Signal Processing for Fast and Precise QEPAS Measurements.

Quartz-enhanced photoacoustic spectroscopy (QEPAS) gas sensors have been widely developed over the last decade. This technique takes the advantage of a high quality factor tuning fork to enable high-sensitivity and high-selectivity miniature gas sensors. Lock-in detection is classically used to measure the resonator amplitude, which is proportional to the gas concentration, but this technique is slow and leads to measurement drifts as it does not follow the resonator frequency drifts over temperature and pressure. This article presents a new QEPAS signal processing technique that allows faster and more stable measurements that will enable accurate and fast multigas sensors.