| 摘要 |
PURPOSE:To enable position detection of high precision by giving an alarm by detecting optically the position of a moving body, moving in proportion to a process variable, by using optical fibers when the moving body approaches a preset position. CONSTITUTION:Opticcal fibers 14 and 17 having projector 19 and photodetector 20, and optical fiber 24 having projector 26 and setter 27 are provided. In addition, prescribed optical switch 23 is provided. In this constitution, reflective mirror M0 fitted to body 12 rotating at a prescribed speed is set in direction Z and while setter 27 is set to a prescribed time, projector 19 is driven. Then, reflected light is photodetected by photodetector 20 and measuring circuit 21 starts counting operation. As rotating body 12 rotates for the set time (angle), optical switch 23 turns off to stop the rotation. When indication piece 11 with reflective mirror M1 moves to this position, reflected light is photodetected by photodetector 20 and circuit 21 stops the counting operation, giving an alarm. Consequently, the alarm can be sent out at prescribed pressure, by previously bearing the relations between outputs of setter 27 and circuit 21 and the pressure scale. |
