Metrology for gas sensors

Gertjan Kok, VSL

Recent years showed a strong increase in the world-wide use of novel low-cost sensors for detection of gases and vapours. Besides well-known applications of gas sensors in air quality and indoor air monitoring, sensors find more and more use in the characterization of new energy gases like biogas and hydrogen (e.g. [1]). For the latter application, both concentrations of the main components as well as of the impurities are relevant.  For the uptake of this technology in domains where absolute accuracy of the measurement data matters, for regulatory purposes (e.g. emissions, air quality) and for health and safety (e.g. hydrogen leakage detection) the quality of the measurement data and sensor reliability need to be carefully considered.

In order to support technology development and market acceptance, the Dutch National Metrology Institute VSL tests the performance characteristics of gas sensors “in situ” by incorporating gas sensors inside a modified and surface-coated cell of a mid-infrared Cavity Ring Down Spectrometer (CRDS). This system is suitable for measuring hydrocarbons, CO, CO2, N2O and due to the special “SilcoNert” coating also reactive species such as HCl, HCN and NH3 down to nmol/mol levels (parts-per-billion). The advantage of VSL’s system is that the sensor and the CRDS spectrometer sample simultaneously the same gas (in a matrix gas that might be e.g. nitrogen, air, methane, natural gas or hydrogen) enabling a real time assessment of the sensor sensitivity and specificity.  Currently, an improved gas sensor test facility is being developed that will allow evaluation of the gas sensor performance and cross sensitivities at a larger variety of conditions of temperature, pressure, relative humidity and wind speed (currently p = 0 to 3 bara, T = 20 to 40 °C, RH = 0 to 300 ppm, v = 0 to 2 m/s, new specs under testing). This poster will present the assessment work (e.g. tests of a metal-oxide sensor with ethanol and a high electron mobility transistor (HEMT) sensor with nitrogen and methane) and the on-going novel developments. [1]  Gersen, Sander. “A control system for all gas compositions.” Enabling Sustainability with Gas: Closing Conference of the Energy Delta Gas Research, Amsterdam, March 2015.

Pen Profile

Gertjan Kok has been working since almost 9 years as Research Scientist at VSL. He has a background in general engineering and applied mathematics, and works on mathematical modelling, data analysis and uncertainty calculations for a variety of applications. In the novel field of gas sensor testing he works on defining test protocols and associated uncertainty calculations. He is also working on the data analysis of measurement results in close collaboration with VSL colleagues performing experimental measurements using a spectroscopic set-up for gas sensor performance testing.

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