Document Type and Number:
Japanese Patent JPS6245497
Kind Code:
B2
Abstract:
A method and an apparatus for transmitting and receiving electromagnetically generated ultra-sound, particularly for non-destructive testing of electrically conductive material, comprising the steps of generating one or more magnetic fields by means of one or more electromagnets (1,2,3,4) and supplying to a transmitter coil (8) in said magnetic field a supersonic frequency, and scanning a receiver coil (52) in said magnetic field. For known apparatuses the signal/noise ratio of a received signal is unfavorable, especially at the testing of non-magnetic material. According to the present invention said ratio is improved in that said magnetic field is generated during a short time compared with the time between two subsequently occurring magnetic fields, and a pulse well-defined in length of supersonic frequency is supplied to the transmitter coil (8) about or at the maximum strength of the magnetic field or fields. The receiver coil (52) thereafter is scanned, but also about or at the maximum strength of the magnetic field or fields. The said pulse has a preferred length of one or two complete sinusoidally-shaped cycles, whereafter the signal is cancelled entirely. According to a preferred embodiment the said pulse is generated through a thyristor-controlled (42) discharge circuit comprising a capacitor (38) and a vacuum gap tube (37). According to a preferred embodiment there is further provided a high-pass filter (53) between the receiver coil (52) and an amplifier (54).
Inventors:
TOOMASU ROBINSON
Application Number:
JP14425779A
Publication Date:
September 28, 1987
Filing Date:
November 07, 1979
Export Citation:
Assignee:
SUTSUDOSUBITSUKU ENERUGITEKUNITSUKU AB
International Classes:
G01N29/04; G01N29/07; G01N29/22; G01N29/24; H03K3/00; H04B11/00