Low cost "laserless" FTIR spectrometer on the farm for real-time nitrous oxide soil emission measurements

A low-cost Fourier transform infrared (FTIR) instrument was developed where the traditional He-Ne reference laser was replaced by a low-cost linear encoder. An RMS sampling error of less than 20 nm was achieved by oversampling both the interferogram and the encoder signal and then resampling the int...

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Bibliographic Details
Published in:Applied optics (2004) 2013-02, Vol.52 (4), p.B93-B101
Main Authors: Haugholt, Karl Henrik, Lacolle, Matthieu, O'Farrell, Marion, Honne, Atle, Bakke, Kari Anne Hestnes, Lundon, Aina
Format: Article
Language:English
Subjects:
Apodization
Coders
Emission analysis
Encoders
Farms
Nitrous oxides
Sampling
Soil (material)
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Summary:A low-cost Fourier transform infrared (FTIR) instrument was developed where the traditional He-Ne reference laser was replaced by a low-cost linear encoder. An RMS sampling error of less than 20 nm was achieved by oversampling both the interferogram and the encoder signal and then resampling the interferogram using a correction table for the encoder. A gas calibration model was developed for the system, which was chosen to have a stroke length of 21 mm and, thereby, a resolution of 0.4 cm(-1) after apodization. The instrument was mounted on a vehicle and employed in an agricultural field test for measuring soil emissions, in particular nitrous oxide (N(2)O). The concentration of N(2)O was measured with a root mean squared error of 6 ppb. The results compared well with lab-based gas chromatography measurements.
ISSN:1559-128X
2155-3165
DOI:10.1364/AO.52.000B93