| 摘要 |
PURPOSE:To improve the pulse response at pulse drive of an ultrasonic oscillator, by connecting a coil oscillating a parallel resonance frequency being approximate to a resonance frequency of the ultrasonic wave oscillator in parallel with the ultrasonic oscillator by means of the static capacitance of the ultrasonic wave oscillator. CONSTITUTION:The ultrasonic wave oscillator 1 has a static capacitance C0, the C0, a capacitor C1 and the inductance of coils L1, L2 consitute a parallel responance circuit and the resonance frequency is designed so as to be close to a resonance frequency f0 of the ultrasonic wave oscillator 1. Since the impedance at a frequency (f) viewed from both ends of the ultrasonic wave oscillator 1 is minimized at the f0, the echo time is reduced remarkably. The capacitor C1 is for temperature compensation and connected in parallel with the ultrasonic wave oscillator 1 so as to reduce the change in the total capacitance and to eliminate the change of the resonance frequency of the parallel resonance circuit comprising the coils L1, L2 due to temperature. Since the transmitted signal is large, diodes D1, D2 are low in the impedance, and since the received output signal is small, the D1, D2 are high in the impedance, and the single ultrasonic wave oscillator 1 is used in common for the receiving and transmission. |
