PROXIMITY SENSOR

摘要

PROBLEM TO BE SOLVED: To prevent the frequency of an oscillation circuit from being limited to be a frequency discriminated by a frequency discrimination circuit with respect to the high frequency oscillation proximity sensor. SOLUTION: The sensor is provided with an oscillation circuit whose frequency changes with a distance up to an object and with a local oscillation circuit 3 that is oscillated at a prescribed local oscillation frequency. A multiplier 2 provides an output denoting the sum or the difference between the outputs of the circuits 1 and 3. A low-pass filter 4 extracts the difference frequency signal obtained by the multiplier 2 and a frequency discrimination circuit 5 discriminates the signal. Then the local oscillation frequency of the local oscillation circuit 3 is selected to select the frequency of the oscillation circuit 1 and then hence the degree of freedom of frequency selection is enhanced.