JPS6416960A - Ultrasonic inspection device - Google Patents

Abstract

PURPOSE:To amplify a received signal consisting of reflected pulses from any distance with low noise and low power consumption without any saturation by providing a transistor (TR), an ultrasonic vibrator, a bias current control part, etc. CONSTITUTION:A bias current control part 40 performs control so that a collector bias current Ic to the TR 1 of a preamplifier has a maximum value ever time an ultrasonic pulse is incident on the ultrasonic vibrator and decreases monotoneously with time until a next ultrasonic pulse is incident thereon. Further, a reflected pulse which is reflected in a body to be inspected to return and has small delay from the point of time of the ultrasonic wave pulse incidence is short in propagation distance and therefore small in attenuation, and the amplitude of the receiving signal is large. For the purpose, the current Ic is made large so as to evade saturation. When the delay is large, on the other hand, the current Ic is made small. Therefore, variation characteristics of the current Ic eliminates saturation with a large-amplitude receiving signal, improves the S/N of the small-amplitude receiving signal, and reduces the power consumption.