Patent ID: 7930925

Claim:
A method for measuring hydrogen concentration in a member comprising the steps of: placing an electromagnetic ultrasonic sensor in the proximity of, or on, the surface of an object to be measured; applying a changing magnetic field to the object to be measured by said electromagnetic ultrasonic sensor; and receiving an ultrasonic wave generated in the object to be measured by said changing magnetic field, the method characterized by comprising the steps of: receiving a longitudinal ultrasonic wave vibrating in the thickness direction of the object to be measured; adjusting the frequency of the changing magnetic field so that said longitudinal ultrasonic wave is caused to resonate; receiving a transverse ultrasonic wave vibrating in the direction parallel to the surface of the object to be measured; adjusting the frequency of the changing magnetic field so that said transverse ultrasonic wave is caused to resonate; detecting a resonance frequency of each of said longitudinal ultrasonic wave and said transverse ultrasonic wave; calculating a resonance property index from the detected resonance frequency of the longitudinal ultrasonic wave and the detected resonance frequency of the transverse ultrasonic wave; and calculating the hydrogen concentration of the object to be measured by comparing the calculated resonance property index and a reference material data storing the relation between the hydrogen concentration in a member of the same specifications as the object to be measured and said resonance property index.