Reducing power consumption via a discontinuous operation of temperature-modulated micro-hotplate gas sensors: Application to the logistics chain of fruit

In this paper a novel sensor operating strategy is introduced. This consists of a discontinuous mode of operating temperature-modulated sensors. The objective is to reduce power consumption while keeping sensor performance high in view of monitoring the conservation stage of apples along the logistics chain. In this approach, the system will consist of a radio frequency identification reader with onboard gas sensors and a flexible tag with temperature and humidity sensors. The gas sensitive part is integrated by an array of Pt-doped and Pd-doped tin and tungsten oxides deposited by drop coating onto silicon micro-machined substrates. By operating sensors at an optimised temperature-modulation mode and by powering them during the measurement phase only, the system shows good potential to integrate a gas monitor for the application envisaged. Excellent results have been obtained, not only in the accurate identification (i.e., 100% success rate) of the gases that are relevant for monitoring apple quality during transport or storage, but also in quantifying the concentration of the species analysed. Additionally, it was shown that measurement time could be dramatically reduced down to 9.5 s if only identification was attempted or down to 39 s if quantification was envisaged. This allows for reducing power consumption without compromising system performance.