| 摘要 |
A speed transducer for measuring the speed of a moving surface comprises a light chopper for alternately completing and breaking the respective light paths between a light source and first and second photodetectors such that the second light path is completed before the first light path is broken. A pulse generator produces a pulse having a duration which is determined by the time interval between completion of the first and second light paths. A converter converts the pulse to a direct current signal proportional to the speed of the moving surface by generating a comparison pulse, the width of which is controllable by a direct current control signal, and comparing the widths of the generator and comparison pulses to produce an error signal which is indicative of the difference in widths. A control signal is generated in response to the error signal which constitutes the desired output when the compared pulse widths are equal. In a second embodiment, the sum of two pulses representing the speed of a rotating surface at two opposed locations is integrated to produce a direct current signal proportional to the concentric rotational speed only.
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