Patent ID: 8159234

Claim:
A proximity sensor comprising: an L-C resonator having a detection coil for detecting an object, and a resonant capacitor connected across said detection coil; an oscillator being configured to oscillate said L-C resonator; an oscillation detector being configured to detect an oscillation of said L-C resonator; and an output circuit being configured to determine whether or not said object exists within a detection range of said detection coil on a basis of said oscillation detected by said oscillation detector, and output a resultant detection signal indicative of the presence of said object within said detection range, said proximity sensor further comprising a burnout detecting means having a time counter and a discriminator, said time counter being configured to obtain a length of a positive voltage period in which a voltage appearing across said resonant capacitor is kept above a predetermined positive voltage, said discriminator being configured to determine a burnout of said detection coil when a length of said positive voltage period detected by said time counter exceeds a half of an oscillation cycle of said L-C resonator, said output circuit being configured to provide a burnout signal indicative of the burnout of the detection coil determined by said discriminator.