LINEAR SCALE

PURPOSE:To measure with high accuracy an absolute movement of a detecting head, by placing a magnetic sensor at a suitable interval, dividing and synthesizing the output voltage of the magnetic sensor, generating plural synthesized output voltages, and executing the counting by A/D conversion. CONSTITUTION:Two magnetic sensors 32 of a detecting head 2 are placed at a pitch of 1/4 of a pitch lambda of a slit. A synthesizing circuit 39 generates synthesized output voltage by vector-synthesizing output voltages A, B of a pair of magnetic sensors 32. An A/D converting circuit 40 generates converted pulses shown in the figures (b)-(g) from the output voltages A, B and the synthesized output voltages X1-X4. A direction discriminating circuit 41 discriminates a moving direction of the head 2 from an AND pulse of an AND pulse of a pulse train XR shown in the figure (h) and a pulse train AD of the figure (b), and NOT of a pulse train XL of the figure (i) and a pulse train AD of the figure (b), and sends out an addition or subtraction pulse to a counter 42. The counter 42 adds or subtracts the pulse from the discriminator 41, and counts and displays an absolute moving extent of the head 2.