Acceleration and drift reduction of MOX gas sensors using active sigma-delta controls based on dielectric excitation

The objective of this paper is to apply a closed-loop control based on dielectric excitation to MOX gas sensors in order to improve their response time. The control implements a feedback loop in which temperature modulations keep constant the sensor reactance, measured at constant temperature. The required fast temperature switching has been implemented on MEMS microhotplates. The mean temperature generated by the control is the new output signal. This technique is applied to an in-house sensor made of WO3 nanowires decorated with gold nanoparticles to detect NH3 and to a commercial MEMS MOX sensor (CCS801).