| 摘要 |
A rotational speed measuring system comprises a rotatable member with calibration segments and a marker portion both provided along the periphery of the rotatable member, pick-ups for producing a pulse train signal in response to passage of the calibration segments and the marker portion when the rotatable member rotates, an electrical circuit for producing calibration pulses and marker pulses in response to the output signals of the pick-ups, a monostable multivibrator responsive to the marker pulse to produce a pulse signal of a predetermined pulse width, and a counter responsive to the calibration pulses for a period of time defined by the pulse width of the pulse signal from the monostable multivibrator. The counter counts the number of the calibration pulses corresponding to calibration segments which are equidistantly spaced from each other, thereby producing an output signal indicative of the rotational speed of the rotatable member with high accuracy.
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