Patent ID: 8836349

Claim:
A sensor comprising: a variable capacitor; a fixed capacitor; an inductor; a switch configured to alternate between a first position that electrically connects the variable capacitor in a parallel electrical circuit with the inductor and a second position that electrically connects the fixed capacitor in a parallel electrical circuit with the inductor; an oscillator configured to generate a periodic signal; and a controller operatively connected to the switch, the oscillator, and the inductor, the controller being configured to: operate the switch to alternate between the first position and the second position; identify a frequency of a first oscillation of the variable capacitor in the parallel electrical circuit with the inductor based on the periodic signal generated by the oscillator when the switch is in the first position; identify a frequency of a second oscillation of the fixed capacitor in the parallel electrical circuit with the inductor with reference to the periodic signal generated by the oscillator when the switch is in the second position; and identify a capacitance of the variable capacitor based on a ratio of the frequency of the first oscillation to the frequency of the second oscillation.