PURPOSE:To discriminate whether tungsten which should not be put into gold as a false gold exists or not, by using the difference of acoustic velocity to observe the rise position of an observation waveform. CONSTITUTION:A transmitting part 5 receives the synchronizing signal from a synchronizing pulse generating part 6 and generates pulses of an electric signal for the purpose of generating an ultrasonic signal to a probe 1. The ultrasonic signal received by the probe 1 is converted to an electric signal, and this electric signal is amplified in a receiving part 8 and is rectified in a detector 9 and is amplified in an amplifier 10 and is supplied to a cathode-ray tude display part 11. Meanwhile, the signal of the synchronizing pulse generating part 6 is supplied to a sweeping circuit 7 and is synchronized with generation of the ultrasonic signal, and the signal waveform is displayed on a cathode-ray tube. In the display part 11, T indicates the transmission waveform, and B indicates the signal waveform which is reflected from the bottom face of a material 3 to be examined and is turned back. In case of observation of waveforms displayed on the cathode-ray tube display part 11, when the observation waveform for gold and the observation waveform for tungsten are displayed on the same time base, they are different in rise position of reflected waveforms from the bottom face, and thus, they are distinguished from each other easily.
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