Proximity sensor and method of changing detection distance

A method of changing a detection distance, by which a proximity sensor changes the detection distance indicating a distance from a coil to a position where a target object can be detected, the proximity sensor comprising an oscillation circuit that comprises the coil and has an oscillation amplitude that changes with a feedback current, a comparing part that compares the oscillation amplitude with a threshold, and a detecting part that detects the target object based on a comparison result of the comparing part, and the method comprising:

• generating a first signal with respect to the voltage value corresponding to the detection distance by a first signal generating part under the oscillation amplitude at a time when the current value of the feedback current as a previous feedback current value stored in a memory, so that the first signal indicates a digital quantity of a voltage value based on the feedback current and a detection distance;
• setting an analog signal converted from the first signal as the threshold by a threshold setting part;
• generating a second signal with respect to the current value of the feedback current at which the oscillation amplitude in the detection distance is at the voltage value indicated by the first signal, so that the second signal indicates a digital quantity of a current value by a second signal generating part based on a detection distance and the first signal, that current value being stored in the memory as the previous feedback current;
• and
• setting an analog signal converted from the second signal as a current value of the feedback current by a current value setting part.