A novel 6-decades fully-analog uncalibrated Wheatstone bridge-based resistive sensor interface

In this paper a novel fully-analog uncalibrated Wheatstone bridge-based topology suitable for wide-range resistive sensors estimation is presented. The proposed interface is an improvement of a work recently proposed by the authors, showing an increase of the operative dynamic range and both system accuracy and sensitivity. Thanks to the use of a simple closed feedback loop, based on an instrumentation amplifier and an inverting integrator, it is possible to easily set two voltage controlled resistor (VCR) values, so to maintain the bridge balancing condition in the case of sensor variation. The use of this configuration allows the sensor estimation for about 6 decades resistive variation (10 Ω–8 MΩ) with a very high accuracy for a wide-range sensor interface (absolute relative error within ±2%). Experimental tests, performed by using a commercial resistive sensor, have shown that, thanks to its high sensitivity value, the interface can reveal and correctly quantify both few ppm carbon monoxide (CO) particles and percentage relative humidity (RH%) variations.