Abstract: A light beam generated by a light source having a wavelength corresponding to the ethanol absorption spectrum, preferably in the wavelength range of 3.28-3.52 ?m or in one or more wavelength ranges 6.49-7.46 ?m, 7.74-8.33 ?m, 8.84-10.10 ?m, 10.7-12.00 ?m, is sent through a measuring space containing a sample of exhaled breath, and then the intensity of the light beam passing through the measuring space is measured. Based on the spectral analysis of the dependence of the light intensity to the alcohol concentration, the concentration of ethanol vapor is determined and the information about the level of the ethanol content is provided to a suitable display or device.

Abstract: A light beam generated by a light source having a wavelength corresponding to the ethanol absorption spectrum, preferably in the wavelength range of 3.28-3.52 ?m or in one or more wavelength ranges 6.49-7.46 ?m, 7.74-8.33 ?m, 8.84-10.10 ?m, 10.7-12.00 ?m, is sent through a measuring space containing a sample of exhaled breath, and then the intensity of the light beam passing through the measuring space is measured. Based on the spectral analysis of the dependence of the light intensity to the alcohol concentration, the concentration of ethanol vapor is determined and the information about the level of the ethanol content is provided to a suitable display or device.

Abstract: A method and system for measuring the concentration of a gas component in a measuring gas a provided. The wavelength of a light source is modulated with a modulation signal at a modulation frequency, while the wavelength is swept over an interaction feature of a sample. The intensity of the light source is further modulated at a wavelength outside the interaction feature with a burst signal, where an N-th harmonic of the burst frequency coincides with an M-th harmonic of the modulation frequency. The light is passed to the sample and thereafter to a detector. The detector output is demodulated at the M-th harmonic, and the demodulated detector output is normalized by calculating the ratio between a demodulated detector output portion derived from the light modulated with the modulation signal and another demodulated detector output portion derived from the light modulated with the burst signal.

Abstract: There is described a method for measuring a concentration of a gas component in a measuring gas, wherein the light of a wavelength tunable light source is passed along a single optical path through a measuring volume containing the measuring gas and a reference cell containing a reference gas to a detector. The reference cell is selected to contain a selected isotope of the gas component to be measured in a known abundance ratio higher than the known natural-abundance isotope ratio of the gas component in the measuring volume; the light source is tuned to sweep the wavelength of the light over the absorption lines of the selected isotope and the remaining gas component; and the concentration of the gas component in the measuring volume is calculated from the ratio of the detector signals at the peaks of the absorption lines, based on Lambert's law and taking into account the known abundance isotope ratios.

Abstract: A method and system for measuring the concentration of a gas component in a measuring gas a provided. The wavelength of a light source is modulated with a modulation signal at a modulation frequency, while the wavelength is swept over an interaction feature of a sample. The intensity of the light source is further modulated at a wavelength outside the interaction feature with a burst signal, where an N-th harmonic of the burst frequency coincides with an M-th harmonic of the modulation frequency. The light is passed to the sample and thereafter to a detector. The detector output is demodulated at the M-th harmonic, and the demodulated detector output is normalized by calculating the ratio between a demodulated detector output portion derived from the light modulated with the modulation signal and another demodulated detector output portion derived from the light modulated with the burst signal.

Abstract: There is described a method for measuring a concentration of a gas component in a measuring gas, wherein the light of a wavelength tunable light source is passed along a single optical path through a measuring volume containing the measuring gas and a reference cell containing a reference gas to a detector. The reference cell is selected to contain a selected isotope of the gas component to be measured in a known abundance ratio higher than the known natural-abundance isotope ratio of the gas component in the measuring volume; the light source is tuned to sweep the wavelength of the light over the absorption lines of the selected isotope and the remaining gas component; and the concentration of the gas component in the measuring volume is calculated from the ratio of the detector signals at the peaks of the absorption lines, based on Lambert's law and taking into account the known abundance isotope ratios.

Abstract: In a wavelength modulation spectroscopy method and system the wavelength of a light source is modulated with a frequency f0. The light of the light source is passed to a sample for interacting and thereafter detected and demodulated at a higher harmonic Nf0. To suppress non-linearities in the modulation of the wavelength of the light source a portion of the light (15) of the light source (14) is passed to a monitor detector (17). The monitor detector output is demodulated at said higher harmonic Nf0, and the modulation of the light source (14) is predistorted at said higher harmonic Nf0 in dependence on said demodulated monitor detector output.

Abstract: In a wavelength modulation spectroscopy method and system the light of a tunable light source is modulated with a frequency f0, while the wavelength is swept over an interaction feature of a sample to be measured. The light of the light source is passed to a sample for interacting and thereafter detected and demodulated at a higher harmonic Nf0. To suppress effects of fluctuations of the optical transmission of the system on the measurement, originating from varying dust loads, high temperature, gas turbulence etc. in the measurement path (3), a burst signal in form of an envelope modulated pilot tone is added to the modulation of the light (1) of the light source (2) synchronously with the wavelength sweeps at a wavelength outside the interaction feature of the sample. The injected burst signal is at the detection frequency Nf0, where N?2, and is detected together with the measured spectrum from the sample and act as absorption normal, which the spectrum can be calibrated against.

Abstract: In a wavelength modulation spectroscopy method and system the light of a tunable light source is modulated with a frequency f0, while the wavelength is swept over an interaction feature of a sample to be measured. The light of the light source is passed to a sample for interacting and thereafter detected and demodulated at a higher harmonic Nf0. To suppress effects of fluctuations of the optical transmission of the system on the measurement, originating from varying dust loads, high temperature, gas turbulence etc. in the measurement path (3), a burst signal in form of an envelope modulated pilot tone is added to the modulation of the light (1) of the light source (2) synchronously with the wavelength sweeps at a wavelength outside the interaction feature of the sample. The injected burst signal is at the detection frequency Nf0, where N?2, and is detected together with the measured spectrum from the sample and act as absorption normal, which the spectrum can be calibrated against.

Abstract: In a wavelength modulation spectroscopy method and system the wavelength of a light source is modulated with a frequency f0. The light of the light source is passed to a sample for interacting and thereafter detected and demodulated at a higher harmonic Nf0.

Abstract: Method and apparatus for spectroscopic measurement of the concentration of a gas in a sample where you detect the intensity of light from a light source (1) passed through the sample (4) and through a reference cell (5) and generates a signal which represents the concentration of the gas. A laser diode (1) constitutes the light source which is locked to the absorption line of the gas at known concentration and pressure contained in a reference cell (5). The laser light with the properly selected wavelength is distributed via optical fibres (2, 3, 6) and/or glass prisms (19, 20) to the reference cell (5) and the sample (4). Non-gas-related transmission variations in the measurement path or in the optics is automatically compensated for by a special laser modulation which generates a time multiplexed reference.