Mismatch and Offset-Voltage Compensation Technique for Current Excitation Based Resistive Sensors Interface

Resistive sensors have been increasingly used in a number of wearable biomedical applications ranging from prosthetic control to electronic skin, thanks to their miniaturized size. However, most resistive sensor systems suffer thermoelectric offset, large baseline resistance, and drift in baseline resistance. In addition, the system should be battery-operated and consume low power. In this paper, we present a pulse current excitation-based half-bridge mixed-signal interface circuit for accurate and high-resolution resistance measurement of resistive sensors. The circuit utilizes synchronous demodulation and a DC-Servo loop to compensate for the offset and mismatch to enhance the accuracy and measurement range. The circuit provides a linear output voltage proportional to the incremental change in sensor resistance. A prototype of the proposed system is developed and tested. The circuit compensates offset-voltage as high as ± 1.4 Volts and the resistance mismatch up to 100 $\mathrm{k}\Omega$ for a supply voltage of 3.3 Volts with an error of less than ± 1%.