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Sensors 2010, 10(5), 4634-4642; doi:10.3390/s100504634

Time Delay for Aerial Ammonia Concentration Measurements in Livestock Buildings

*  and
Department of Biosystems Engineering, University of Aarhus, Faculty of Agricultural Sciences, Blichers Alle 20, DK-8830 Tjele, Denmark
* Author to whom correspondence should be addressed.
Received: 1 March 2010 / Revised: 29 March 2010 / Accepted: 15 April 2010 / Published: 4 May 2010
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Correct measurements of ammonia concentration in air still present considerable challenges. The high water solubility and polarity can cause it to adsorb on surfaces in the entire sampling system, including sampling lines, filters, valves, pumps and instruments, causing substantial measuring errors and time delays. To estimate time delay characteristics of a Photo Acoustic Multi Gas Monitor 1312 and a Multi Point Sampler continuous measurement of aerial ammonia concentrations at different levels was performed. In order to obtain reproducible data, a wind tunnel was used to generate selected concentrations inside and a background concentration representing the air inlet of the tunnel. Four different concentration levels (0.8 ppm, 6.2 ppm, 9.7 ppm and 13.7 ppm) were used in the experiments, with an additional outdoor concentration level as background. The results indicated a substantial time delay when switching between the measuring positions with high and low concentration and vice versa. These properties may course serious errors for estimation of e.g. gas emissions whenever more than one measuring channel is applied. To reduce the measurement errors, some suggestions regarding design of the measurement setup and measuring strategies were presented.
Keywords: photo acoustic spectroscopy; ammonia measurement; time delay photo acoustic spectroscopy; ammonia measurement; time delay
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Rom, H.B.; Zhang, G.-Q. Time Delay for Aerial Ammonia Concentration Measurements in Livestock Buildings. Sensors 2010, 10, 4634-4642.

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