This paper proposes and analyses a microcontroller-based interface circuit for inductive sensors with
a variable self-inductance. Besides the microcontroller (C) and the sensor, the circuit just requires an
external resistor and a reference inductor so thattwo RL circuits are formed. The C appropriately excites
such RL circuits in order to measure the discharging time of the voltage across each inductor (i.e. sensing
and reference) and then it uses such discharging times to estimate the sensor inductance. Experimental
tests using different commercial Cs at different clock frequencies show the limitations (especially, due
to parasitic resistances and quantisation) and the performance of the proposed circuit when measuring
inductances in the millihenry range. A non-linearity error lower than 0.3% full-scale span (FSS) and a
resolution of 10 bits are achieved, which are remarkable values considering the simplicity of the circuit.