Uncalibrated Analog Bridge-Based Interface for Wide-Range Resistive Sensor Estimation

In this letter we present a simple analog interface for the automatic and continuous estimation of wide-range resistance variations of a sensor whose baseline is unknown. The proposed circuit topology, based on the Wheatstone bridge, is an uncalibrated configuration which employs suitable feedback blocks providing the bridge balancing condition through the substitution of one of the bridge resistors by means of a voltage controlled resistor capable to compensate sensor variations. Experimental results conducted on a PCB have shown that the proposed circuit is able to work for a wide resistive sensor base-line and/or for more than 3 decades of resistance variations (e. g., 300 Omega divided by 700 k Omega, the range is settable), showing a reduced relative error (lower than 1.5%).