| 摘要 |
PURPOSE:To drive a vibrator at an excitation frequency equal to the natural vibration frequency of the vibrator at all times by vibrating the vibrator forcibly and freely repeatedly by turns, detecting the frequency of the vibration of the vibrator in the free vibration period, and correcting next forcible vibration to the detected frequency and equalizing the frequency. CONSTITUTION:When a piezoelectric element 2 for driving is driven with an AC voltage of the oscillation frequency of a voltage-controlled oscillator 7 and a tuning fork 1 is vibrated forcibly at the frequency, the output of this frequency of an oscillator 7 is applied to the element 2. Then when the output of a rectangular wave oscillation circuit 12 falls to zero, the driving voltage to the element 2 is cut off and the tuning fork 1 vibrates automatically at its natural frequency. A piezoelectric element 3 for excited vibration detection detects the natural frequency of the tuning fork in the period of said free vibration and a phase comparator 4 compares it with the oscillation frequency of the oscillator 7. Here, a next rectangular wave from the circuit 12 arrives, and the forcible vibration is started again. The current vibration frequency is the current actual natural vibration frequency of the tuning fork 1 and the amplitude of the forcible vibration is adjusted 9 automatically according to the output of the element 3 to become constant. |
