| 摘要 |
PURPOSE:To detect a rotational speed highly precisely by providing a reflecting part and a nonreflecting part in stripes on the surface of the rotary shaft of the rotary machine such as a steam turbine. CONSTITUTION:A belt-shaped reflecting substance 2 with the reflecting part 2a and the nonreflecting part 2b both having very narrow width W arranged in stripes alternately therein is wound round the periphery of the surface of the turbine shaft 1 of a steam turbine, very fine laser beams are applied from an emitting device 3 to the reflecting substance 2, the laser beams reflected therefrom are received by a photoreceiving device 4, and further pulse signals from this photoreceiving device 4 are counted every prescribed time t by a counter 5, whereby detection of the rotational speed of the turbine is performed. |
