Abstract: A combined gas sensor device allowing the measuring of the concentration of a gas by tunable diode laser spectrometry as well as by resonant photo-acoustics within one housing. A laser beam used for laser spectrometry is sent across the openings of a measuring cell usually used for resonant photo-acoustic determination. Thus, both measuring principles use the same gas sensing module with a minimum of space consumption, so that the device can be produced with minimum dimensions. Further, a common opto-electronics and electronics platform can be used which reduces the overall costs of such a combined gas sensor.

Abstract: A method for performing quartz-enhanced photoacoustic spectroscopy of a gas, includes providing a light source configured to introduce a laser beam having at least one wavelength into the gas such said at least one molecule within in the gas is stimulated generating an acoustic signal, accumulating the acoustic signal in a resonant acoustic detector, generating a resonant absorption signal (SA) relative to the gas concentration by at least one tuning fork serving as resonant acoustic detector, generating additionally a resonant intensity signal (SI) proportional to the intensity of the laser beam travelling through the gas, and providing an output signal (SGC) from said absorption signal (SA) and said intensity signal (SI) being independent of the intensity of the light relative to the presence or concentration of the gas.

Abstract: A method for etalon suppression in a gas detection device by determining an etalon fringe period during a calibration step without gas in dependency of the DC drive current. A measuring signal which is a function of the gas absorption and substantially independent of an intensity modulation of an initial light signal at an initial frequency (f) is generated by determining a first pre-measuring signal when the laser source is operated at the center of the gas absorption peak, a second pre-measuring signal when the laser source is operated with a DC drive current below the gas absorption peak of the gas to be detected, and a third pre-measuring signal when the laser source is operated with a DC drive current above said gas absorption peak, with a difference between said DC drive currents which corresponds to the etalon fringe period determined in a calibration step before.

Abstract: The gas detector device comprises at least a VCSEL source and at least a light sensor for detecting a light beam having passed through a sample chamber containing a given gas to be detected. The detection signal of the sensor directly provided to or is time derivated by an electronic derivator and then provided to respective lock-in amplifiers in order to generate a two different 2f-detection, f being the frequency of a wavelength modulation of the source, and thus to provide two corresponding measuring signals the division of which gives a precise value of the gas concentration. The invention uses at least a first modulation reference signal at twice and a second modulation reference signal at twice of the modulation frequency of the laser source.