| 摘要 |
PURPOSE:To accurately obtain 90 deg. as the phase difference between a sum and a difference signal found from the outputs of two magnetic heads which are almost electrically 90 deg. out of phase with a magnetic scale by varying the phase difference relatively by adjusting exciting currents to the magnetic heads. CONSTITUTION:The two magnetic heads 2 and 3 are arranged at a nearly 90 deg. angle to the magnetic scale 1. The outputs e1 and e2 of the magnetic heads 2 and 3 are added 17 and subtracted 19 to obtain signals eA and eB. The oscillation frequency of a reference signal oscillator 4, on the other hand, is divided 5 to 1/2n and the low-frequency component is extracted by an LPF 6 and amplified 7 and passed through variable shunting circuits 21 and 22 to adjust the exciting currents to exciting coils 2A and 3A, thereby setting the phase difference between the composite output signals eA and eB accurately to 90 deg.. Consequently, the accurate phase difference of 90 deg. is easily obtained. This is suitable to a phase detection type magnetic scale.
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