Dual cantilever enhanced photoacoustic detector with pulsed broadband IR-source

The cantilever enhanced photoacoustic (CEPA) trace gas detection was combined with an electrically modulated broadband infrared (EMBIR) source. The high sensitivity of the detection method was further improved by using two cantilever sensors on the opposite walls of the photoacoustic cell in order to suppress noise. Methane (CH4) gas was used to demonstrate the sensitivity of the method yielding a detection limit of 0.5 ppm with 5 s sample integration time employing an optical filter with a center wavenumber 2950 cm−1. The achieved result is very good with a low power infrared source and enables the utilization of the benefits of such a source: low price and power consumption, easily controlled and simple electrical modulation of the radiation intensity and absence of the mechanical chopper and its noise. The structure of the source enables a relatively high pulse rate to be used as the modulating frequency. Optical filters can be used to select the wavenumber region for the selective detection of different gases.