POSITION DETECTOR

PURPOSE:To detect a recessed part provided on the surface of an object by an inexpensive method as compared with the conventional method using a TV camera, by using an electromagnetic analog sensor for the detection. CONSTITUTION:The detecting head 1 of an electromagnetic analog sensor 2 is moved along the upper surface of an object 3. The sensor 2 radiates a high-frequency magnetic field toward the object 3 and produces an eddy current corresponding to the distance between the object 3 and detecting head 1. When a recessed part 3a exists on the upper surface of the object 3, the eddy current output of the detecting head 1 varies and a control section 4 calculates the distance between the detecting head 1 and the recessed part 3a. On the other hand, a displacement meter 7 detects the position of the detecting head 1. Outputs from the control section 4 and displacement meter 7 are inputted in a controller 6 through AD converters 5 and 8. The controller 6 calculates the position of the recessed part 3a from the two information.