Patent ID: 8826739

Claim:
An ultrasonic measuring method for measuring a thickness of a coating material applied by coating to one surface or both surfaces of a substrate made of a metal so as to provide a coated product, comprising: providing a pair of first ultrasonic sensor and second ultrasonic sensor; placing the first ultrasonic sensor on one side of the coated product, as viewed in a thickness direction of the coated product, via an air layer, and placing the second ultrasonic sensor on the other side of the coated product, via an air layer; and measuring the thickness of the coating material by transmitting ultrasonic waves between the first ultrasonic sensor and the second ultrasonic sensor, wherein a flat-type transmitting sensor that permits propagation of unfocused ultrasonic waves is used as the first ultrasonic sensor, and a flat-type receiving sensor that permits propagation of unfocused ultrasonic waves is used as the second ultrasonic sensor; a receiving-side ultrasonic sensor as one of the first ultrasonic sensor and the second ultrasonic sensor, which receives ultrasonic waves propagated through the air layer, generates a plurality of sonic waveforms as time passes after receiving the ultrasonic waves, said plurality of sonic waveforms including a first sonic waveform that is detected first, and a second sonic waveform that is detected subsequent to the first sonic waveform; and respective frequencies of the first ultrasonic sensor and the second ultrasonic sensor are set to the lowest possible levels, according to the thickness of the coating material, under a condition that the second sonic waveform and the first sonic waveform do not overlap each other.