A direct approach for interfacing four-wire resistive sensors to microcontrollers

Abstract

Abstract In the field of direct sensor-to-microcontroller interface circuits, a novel proposal for four-wire connected resistive sensors is suggested and experimentally tested herein. The circuit relies on measuring six discharging times corresponding to six RC circuits, which include the sensor resistance and the parasitic resistance of the wires. The circuit has been applied to measure resistors emulating a Pt100 thermal sensor with different values of wire resistance. Experimental results show that the accuracy and linearity of the proposed circuit is not deteriorated while increasing the wire resistance, either by the mismatch between the wire resistances. The error, with respect to the case with null wire resistances, is lower than 45 mΩ, while the non-linearity error is lower than 0.05% full-scale span in the worst scenario under test.