Method for measuring the resonant frequency of photoacoustic detector in the real-time mode

A method for measuring the resonant frequency of a photoacoustic detector (PAD) in the realtime mode in a wide temperature and gas-mixture-composition range is proposed. The method is based on measurements of natural frequencies of the resonance PADs, which are excited using an auxiliary acoustic emitter built into the PAD. The measurement procedure takes ≤0.1 s. When the PAD is filled with air or nitrogen, the high accuracy and reproducibility of the measurement results is experimentally shown. The relative measurement error of the PAD resonant frequency (~1700 Hz) is approximately 6 × 10 –5 .