| 摘要 |
PURPOSE:To make it possible to measure a minute rotary angle, by obtaining th rotary angle from the number of elastic surface waves, which are included in the rotary angle, when an elastic surface wave converter having an interdigital electrodes, which cause elastic surface waves, on the outer surface of a ring shaped piezoelectric body, is rotated. CONSTITUTION:A piezoelectric body 1 is formed in a ring shape having an outer diameter of 37.5mm., an inner diameter of 33.5mm., and a height of 10mm. by using, e.g., lead titanate zirconate. Interdigital electrodes 2 comprising pectinated conductors 2a and 2b are attached and formed by the evaporation of silver on the outer surface of the piezoelectric body 1. Thus an elastic surface wave converter T is formed. The converter T is incorporated into an oscillator circuit R. For example, a resonance frequency of 1.93MHz at 2V is applied on the electrodes 2, and elastic surface waves are propagated along the outer surface of the piezoelectric body 1. The number of waves is counted by a optical heterodyne method, and the number of waves of 120 is obtained as a total (360 deg.). Thus the rotary angle can be detected by the counted number of the waves.
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