Influence of carrier gas on microwave gas response Detection of ammonia in air/argon.

The impact of carrier gas species on the response of microwave gas sensor at room temperature is estimated in this paper. The microwave transduction is a good candidate for embedded sensing devoted to Internet of Things. The sensing characteristics are investigated (drift of the baseline, reversibility, recovery time, kinetics) with air and argon flow. Ammonia is chosen for the detection in a wide range of concentration [20 -500 ppm] according to the various cases in agri-food, petrochemical and freezing applications. The substrate is flexible (Duroid). The used sensitive material is TiO2 super-substrate on a microstrip spiral resonator. The pattern is a trapezoidal spiral working in wide-band of frequencies [1-8 GHz]. In these conditions of sensing, the kinetic of adsorption and desorption and its order are evaluated. Sensing mechanisms are discussed.