Measurement of the Thickness of Metal Plate by Ultrasonic Harmonic Method. II : Electronic Operation and Results of a Field Inspection

In this paper, which deals with the technical descriptions of the apparatus to extend as far as possible the range of practical application of this method, the writer has proceeded with the design of the measuring circuit. After giving some important technical notes on the arrangements of the circuit, the construction of the apparatus made by the writer has been presented. The accuracy and possibility of this measurement should be considered under various conditions of the metal plate to be tested, and so, with the some samples indented or sloped in the back surface, indications of the thickness resonance have been discussed experimentally. Lastly, as a typical example of the practical application of this method, the inspection of the wall thickness of the penstock at the electric power plant has been adduced. Readings at some points in this inspection have been compared with the direct readings obtained by the drilling method. The difference between the readings by the two ways is less than six percent at every point