MEASURING APPARATUS OF OUTER DIAMETER OF STEEL PIPE

PURPOSE:To easily measure the outer diameter of a steel pipe by a method wherein a transmitting and a receiving probes are brought into touch with the surface of the steel pipe with use of the surface wave of ultrasonic waves, and the outer diameter of the steel pipe is calculated from the propagating time of the ultrasonic waves between both probes. CONSTITUTION:A transmitting electric pulse which is generated at a transmitting part 5T at the transmitting timing given from a reference clock generating part 6 is, through a cable 4T, converted to an ultrasonic wave at a transmitting ultrasonic probe 2T. The ultrasonic wave sent out of the probe 2T is propagated on the surface of a steel pipe 1 and received by a receiving ultrasonic probe 2R, where it is converted to an electric signal. The electric signal from the probe 2R is transmitted to a propagating time measuring part 7 via a cable 4R and a receiving part 5R. In the measuring part 7, reference clocks from when the transmitting pulse is generated from the transmitting part 5T to when the echo is received from the receiving part 5R are counted, thereby to obtain the propagating time (t). In an outer diameter operating part 8, the propagating distance X is obtained from the time (t) and the sound speed V of the surface wave in the steel pipe, and the outer diameter of the steel pipe 1 is accordingly calculated at 9 from the time (t) and distance X.