| 摘要 |
PURPOSE:To detect the number of rotations with good accuracy, by a method wherein noise in the waveform of the pulsating current of a motor is removed and the peak value of the pulsating waveform is held to compare it in a comparator with hysteresis as a reference voltage. CONSTITUTION:A resistor 2 is inserted between a DC motor 1 and a DC power source 3 and the amount V1 of voltage drop (corresponding to the pulsating current of the motor 1) is removed by a noise removing circuit 6 through the resistor 4, a Zener diode 5 to remove a noise. A pulsating waveform V2 is amplified by an AC current amplifying circuit 7, the peak value is held by a peak hold circuit 8 and is divided through resistors 9 to obtain a reference voltage V6. The reference voltage V6 is compared with the pulsating waveform V2 in a comparating circuit 10 with hysteresis. According to this method, each pulsation may be taken out surely one by one as a pulse output V4 even when there is pulsating fluctuation whereby the number of rotations of the DC motor 1 may be detected with a good accuracy. |
