n this work we have presented two configuration schemes representing fully analog and automatic Wheatstone bridge-based interfaces that largely extends the operating interval of the traditional bridge. Thanks to the reading of only one voltage output signal and the use of a four quadrant multiplier as VCR, it is possible to easily estimate wide resistive sensor variations for different circuit bridge-based topologies.
Results derived from gas sensing estimation have shown that the interface is able to detect small (ppm) carbon monoxide quantities. It must be discussed that circuit response with accurate sample resistive load provides always the same results; on the contrary with the air quality sensor employed, sensor response strictly depends on environment (e.g. temperature and humidity). However, once defined circuit response with sensor baseline, it was capable to correctly detect few CO particles and relative humidity. Moreover, to confirm the theory, a WO3 resistive sensor, whose heater temperature has been changes so to obtain a wide-range baseline variation (0–250 °C), has been also employed.
The achieved results have demonstrated that gas sensors in combination with suitable interface circuits are promising candidates for the implementation of low-cost gas-sensing systems.