| 摘要 |
PURPOSE:To vary an ultrasonic transmission level at a high speed by varying the screw rate of a switching element, varying the degree of the sharpness of the rising of a driving pulse waveform supplied to an ultrasonic vibrator, and controlling the ultrasonic wave transmission level. CONSTITUTION:A coupling capacitor C2 is charged to a voltage equal to a source voltage (100V) right before a transmission trigger pulse is applied. When a transmission trigger pulse is applied to the 1st gate G1 of an FETQ1, the FETQ1 turns on, but a resistance R1 is sufficiently large, so vibrator TD and the FETQ1 operates as a load on the capacitor C2, so that a voltage VD supplied to the FETQ1 drops by the discharging of the capacitor C2. The discharging in this period depends upon the current limit value in the constant current area of the FETQ1 and a voltage which varies like this is applied to the vibrator TD. Then, a voltage Vg2 is set to a desired screw rate value through an amplifier A2 corresponding to target investigation vibration and the transmission trigger pulse is applied to a gate G1 to generate an ultrasonic wave with a transmission level matching with different depth by the vibrator TD while the source voltage is still constant.
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