| 摘要 |
PURPOSE:To detect with good accuracy the speed at a low speed revolution without increasing the capacity of a counter by counting the pulse transmitted from a pulse generator by a counter and by counting one of the output of two oscillators generating the prescribed frequency by another counter during the period upto the generation of the following pulse after the passing of a fixed time. CONSTITUTION:Oscillators 15, 16 generates the fixed frequency which is sufficiently higher than the frequency outputted at the time when the pulse generation is in the highest or lower number of revolutions. With the input of a START signal an FF12 starts the count of the output of the oscillator 15 with actuating a counter 18 by the rise of the output ENP of the pulse generator and counts the ENP only for a fixed time T with actuating a counter 19 by the output thereof. A counter 20 is actuated via FF13, 14 with the output of the counter 18 and the output of the oscillator 15 or 16 is respectively counted until the following rise of ENP after the lapse of the T via a switching circuit 17 according to the high speed or low speed revolution. A computing element 24 calculates the revolution speed from these count values and T. |
