| 摘要 |
PURPOSE:To detect for sure if any noise is mixed in or not in a rotational speed detector by setting two different slice levels for an electromagnetic pickup output and by the correspondence of output when the rotational speed is over a set speed. CONSTITUTION:The output of an electromagnetic pickup 1 is detected based on slice levels S1 and S2 (S2>S1) by calculation circuits 11 and 14 and is converted into rotational speed n1 or n2. The level S1 is set up so that the output wave height value reaches it at a low speed rotation A, and the level S2 is set up higher enough that an expected noise levels and high enough so that wave height value reaches it at a high speed rotation (=N) B. In the low speed area where n1<N2, rotational speed n1 is adopted. If n1not equal to N2, in the high speed area where n1>=N2, noises detected only by the level S1 is judged to be included in n1 and alarm 20 is issued, and n2 is adopted as the rotational speed. |
