Measuring and testing – Vibration – By mechanical waves
Patent
1979-10-31
1981-12-29
Ciarlante, Anthony V.
Measuring and testing
Vibration
By mechanical waves
G01N 2904
Patent
active
043076157
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
oise 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).
REFERENCES:
patent: 4164873 (1979-08-01), Bottcher et al.
Ninth World Conference on Non-Destructive Testing, "Electromagnetic Generation of Ultrasonic Waves in Absence of External Magnetic Field and its Applications to Steel Production Lines," Kawashima et al., 11/79.
Ciarlante Anthony V.
Studsvik Energiteknik AB
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