| 摘要 |
PURPOSE:To make it possible to measure a wall thickness of 3mm or less, by operating the cycle sowing the max. spectrum component in a specific frequency component according to a specific formula. CONSTITUTION:An electromagnetic ultrasonic wave sensor 7 is driven by a conventional wall thickness measuring device 8 and a multiple echo interval or the time interval (r) between an incident wave and a first echo is measured by the measuring device 8 and a wall thickness W is calculated from W=vXrX1/2 (v is sonic velocity) to be displayed on a display part 13 through a control apparatus 12. When a wall thickness is 3mm or less, a wall thickness measured value becomes infinity . When the measured value infinity is sent from the measuring device 8, the control apparatus 12 operates a calculator 10. The calculator 10 digitally reads a received wave form by the operation order from the control apparatus 12 to store the same in a memory 11. Then, the absolute value of each frequency component is calculated on the basis of the value stored in the memory 11 according to a preliminarily stored Fourier transformation formula and the frequency f0 showing the max. value in said frequency components is calculated. Next, the repeating cycle T of an ultrasonic pulse is calculated from T=1/f0 and a wall thickness to is calculated according to formula.
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