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Title: Ammonia sensing system based on wavelength modulation spectroscopy
Authors: Carlos Duarte Viveiros
João Ferreira
Susana Oliveira Silva
José Luís Santos
Orlando Frazão
José Manuel Baptista
Issue Date: 2015
Abstract: A sensing system in the near infrared region has been developed for ammonia sensing based on the wavelength modulation spectroscopy (WMS) principle. The WMS is a rather sensitive technique for detecting atomic/molecular species, presenting the advantage that it can be used in the near-infrared region by using the optical telecommunications technology. In this technique, the laser wavelength and intensity were modulated by applying a sine wave signal through the injection current, which allowed the shift of the detection bandwidth to higher frequencies where laser intensity noise was typically lower. Two multi-pass cells based on free space light propagation with 160 cm and 16 cm of optical path length were used, allowing the redundancy operation and technology validation. This system used a diode laser with an emission wavelength at 1512.21 nm, where NH<inf>3</inf> has a strong absorption line. The control of the NH<inf>3</inf> gas sensing system, as well as acquisition, processing and data presentation was performed. © 2015, The Author(s).
metadata.dc.type: article
Appears in Collections:Non INESC TEC publications - Articles in International Journals

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