| 摘要 |
PURPOSE:To measure automatically the fundamental frequency of a signal to be measured which contains higher harmonics by providing a pulse converting circuit for the signal to be measured which consists of a differentiating circuit, an output pulse width control circuit for a one-shot multivibrator, etc. CONSTITUTION:The differentiating circuit 7 outputs a positive pulse when a binary-coded signal (b) outputted by a binary coding circuit 1 rises and the one-shot multivibrator 8 outputs a positive pulse (d) with depth determined by a control circuit 9 every time a pulse is inputted to its input (c). A reference frequency oscillation circuit 2 generates a reference frequency. A gate control circuit 4 holds the opening time of a gate circuit 5 constant with a reference clock which is frequency-divided by a frequency dividing circuit 3. When a reset signal (f) is inputted, the control circuit 9 begins to narrows down the output pulse width of the multivibrator 8 continuously from its maximum value and when the negative pulse is outputted, the current pulse is held to output a gate opening permission signal (g). The circuit 4 opens the gate 5 for a time determined by the reference frequency after the signal (g) is inputted, and pulses which are inputted within the time are counted 6. |
