Measuring and testing – Instrument proving or calibrating – Volume of flow – speed of flow – volume rate of flow – or mass...
Patent
1982-09-30
1984-05-01
Birmiel, Howard A.
Measuring and testing
Instrument proving or calibrating
Volume of flow, speed of flow, volume rate of flow, or mass...
73584, 367 13, H04B 1300, H04R 2900
Patent
active
044453612
ABSTRACT:
Apparatus and method for nondestructive detection of loose parts or faulty onds in sound transducers by measuring erratic second-order nonlinear difference-frequency responses of the test transducer to a pulsed high level dual-frequency sound field produced by a high power projector. Such field may be generated by combining a high frequency carrier signal at frequency f.sub.o with a low frequency tone burst signal at frequency f/2 in a double balanced modulator so as to produce the dual-frequency pulse at f.sub.o +f/2 and f.sub.o -f/2. The test transducer converts the dual-frequency pulse into a plurality of linear and nonlinear frequency components including the difference-frequency f. These are then fed through a passive low-pass filter to eliminate the high frequency components, amplified by a pre-amplifier, further filtered by a bandpass filter to eliminate the DC component, leaving only the difference-frequency f which is amplified by a post-amplifier and displayed on a cathode-ray oscilloscope triggered by synchronizing pulses from the tone burst oscillator. Rapid variations in the difference-frequency signal level and phase indicate a loose part or bond.
REFERENCES:
patent: 3036289 (1962-05-01), Beebe et al.
patent: 3659255 (1972-04-01), Trott
patent: 3781776 (1973-12-01), Kuhn et al.
patent: 4391124 (1983-07-01), Drost
Konrad William L.
Moffett Mark B.
Beers Robert F.
Birmiel Howard A.
McGill Arthur A.
McGowan Michael J.
The United States of America as represented by the Secretary of
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