| 摘要 |
PURPOSE:To detect simply an excess of a speed by taking a conjunction of an output of a monostable multivibrator triggered by an input pulse having a cycle corresponding to the speed, and of an output of a memory memorizing the output of the monostable multivibrator synchronously with the input pulse. CONSTITUTION:A pulse Pf having a frequency proportional to a speed of rotation is supplied to a retrigger-type monostable multivibrator 2 and triggered therein by a fall of the pulse Pf, while it is supplied to the clock terminal of a D-FF circuit 3. The time constant tauM of the monostable multivibrator 2 is selected beforehand to be nearly equal to a cycle of the pulse Pf at the time when the speed of rotation is the one to be detected. Then, when an output MQ of the monostable multivibrator 2 is supplied to a terminal D of the D-FF circuit 3, the output of the monostable multivibrator 2 is sampled by a rise of the pulse Pf, and when the pulse Pf becomes larger than the time constant tauM, a signal FQ which falls at the time point of the pulse just after that is obtained. When the conjunction of the output MQ and the signal FQ is taken, a detection signal as to whether the speed of rotation is less than a prescribed speed or not can be obtained. |
