Publication

Ammonia trace measurements at ppb level based on near-IR photoacoustic spectroscopy

Luc Thévenaz, Jean-Philippe Besson
2006
Journal Articles

Abstract

A photoacoustic sensor using a laser diode emitting near 1532 nm in combination with an erbium-doped fibre amplifier has been developed for ammonia trace gas analysis at atmospheric pressure. NH3 concentration measurements down to 6 ppb and a noise-equivalent detection limit below 3 ppb in dry air are demonstrated. Two wavelength-modulation schemes with 1f and 2f detection using a lock-in amplifier were investigated and compared to maximise the signal-to-noise ratio. A quantitative analysis of CO2 and H 2O interference with NH3 is presented. Typical concentrations present in ambient air of 400 ppm CO2 and 1.15% H 2O (50% relative humidity at 20 °C) result in a NH3 equivalent concentration of 36 ppb and 100 ppb, respectively. © Springer-Verlag 2006.

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https://infoscience.epfl.ch/entities/publication/538b49d1-e80e-42be-b4c5-a71e98939a78

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Luc Thévenaz, Jean-Philippe Besson
2006
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/538b49d1-e80e-42be-b4c5-a71e98939a78

About this result

Related concepts (32)

Noise figure

Noise figure (NF) and noise factor (F) are figures of merit that indicate degradation of the signal-to-noise ratio (SNR) that is caused by components in a signal chain. These figures of merit are used to evaluate the performance of an amplifier or a radio receiver, with lower values indicating better performance. The noise factor is defined as the ratio of the output noise power of a device to the portion thereof attributable to thermal noise in the input termination at standard noise temperature T0 (usually 290 K).

Ammonia

Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous waste, particularly among aquatic organisms, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to 45% of the world's food and fertilizers. Around 70% of ammonia is used to make fertilisers in various forms and composition, such as urea and diammonium phosphate.

Signal-to-noise ratio

Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to noise power, often expressed in decibels. A ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise. SNR is an important parameter that affects the performance and quality of systems that process or transmit signals, such as communication systems, audio systems, radar systems, imaging systems, and data acquisition systems.

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