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Exploiting plume structure to decode gas source distance using metal-oxide gas sensors

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Original languageEnglish
Pages (from-to)636-646
Number of pages11
JournalSensors and Actuators B: Chemical
Volume235
DOIs
Publication statusPublished - 1 Nov 2016

Abstract

Estimating the distance of a gas source is important in many applications of chemical sensing, like e.g. environmental monitoring, or chemically-guided robot navigation. If an estimation of the gas concentration at the source is available, source proximity can be estimated from the time-averaged gas concentration at the sensing site. However, in turbulent environments, where fast concentration fluctuations dominate, comparably long measurements are required to obtain a reliable estimate. A lesser known feature that can be exploited for distance estimation in a turbulent environment lies in the relationship between source proximity and the temporal variance of the local gas concentration - the farther the source, the more intermittent are gas encounters. However, exploiting this feature requires measurement of changes in gas concentration on a comparably fast time scale, that have up to now only been achieved using photo-ionisation detectors. Here, we demonstrate that by appropriate signal processing, off-the-shelf metal-oxide sensors are capable of extracting rapidly fluctuating features of gas plumes that strongly correlate with source distance. We show that with a straightforward analysis method it is possible to decode events of large, consistent changes in the measured signal, so-called 'bouts'. The frequency of these bouts predicts the distance of a gas source in wind-tunnel experiments with good accuracy. In addition, we found that the variance of bout counts indicates cross-wind offset to the centreline of the gas plume. Our results offer an alternative approach to estimating gas source proximity that is largely independent of gas concentration, using off-the-shelf metal-oxide sensors. The analysis method we employ demands very few computational resources and is suitable for low-power microcontrollers.

Notes

This document is the Accepted Manuscript version of the following article: Michael Schmuker, Viktor Bahr, & Ramon Huerta, ‘Exploiting plume structure to decode gas source distance using metal-oxide gas sensors’, Sensors and Actuators B: Chemical, Vol. 235: 636-646, November 2016, doi: http://dx.doi.org/10.1016/j.snb.2016.05.098. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/. Published by Elsevier.

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