| 摘要 |
PURPOSE:To detect the rotating speed of the inside rotating body of double rotary facilities precisely with a simple constitution by emitting luminous flux toward the light beam shield member of the inside rotating body and photodetecting the luminous flux at the opposite side of the light beam shield member. CONSTITUTION:A twister 22 and light beam shield plates 34A-34C, a low-pass filter 40, a waveform shaping circuit 42, a frequency counter 44, etc., are provided. The output of a photodetecting element 36 is amplified 38 and inputted to the filter 40. Further, the cutoff frequency fc of the filter 40 is set automatically to a value proportional to the rotating speed Nt of the twister 22 measured by a twister speed indicator 46. Then the output waveform of the filter 40 is supplied to the circuit 42 to shape its waveform. The output of the circuit 42 is counted 44 and its output is divided by the number of the shield plates 34A-34C to measure the rotating speed of an overtwister 26 accurately.
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