Patent US4445361A successfully refreshed from Google Patents.
US4445361A
Expired / Lapsed
US
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System for detection of transducer defects
Assignee: United States Department of the Navy
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Filing: 1982-09-30
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Granted: 1984-05-01
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Expires: 2002-09-30
Abstract
Abstract Apparatus and method for nondestructive detection of loose parts or faultyonds 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 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 o +f/2 and f 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.
Inventors
- 👤 Mark B. Moffett
- 👤 William L. Konrad
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 09:29
CPC Classifications
G; G01; G01H; G01H3/00; G01H3/005; G01V; G01V13/00
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
172 words
An apparatus for detecting defects in transducers under test, comprising: frequency generating means for producing a synchronizing pulse and a dual-frequency signal at frequencies f o +f/2 and f o -f/2 where f o >>f/2; a projector, submerged in water and connected to said frequency generating means, for receiving said dual-frequency signal from said frequency generating means and projecting said dual-frequency signal a short distance through the water to said test transducer, said test transducer thereafter producing output frequencies f o +f/2, f o -f/2, 2f o , 2f o +f, 2f o -f, f, and a DC component in response thereto; a linear, difference-frequency filtering means for receiving said output frequencies from said test transducer and producing as the output thereof only difference-frequency f; and display means, connected to said difference-frequency filtering means and said frequency generating means, for receiving said difference-frequency f from said difference-frequency filtering means and said synchronizing pulse from said frequency generating means, and displaying said difference-frequency f thereon thus permitting observation and measurement of signal characteristics.
Claim 2
Independent Claim
172 words
An apparatus for detecting defects in transducers under test, comprising: frequency generating means for producing a synchronizing pulse and a dual-frequency signal at frequencies f o +f/2 and f o -f/2 where f o >>f/2; a projector, submerged in water and connected to said frequency generating means, for receiving said dual-frequency signal from said frequency generating means and projecting said dual-frequency signal a short distance through the water to said test transducer, said test transducer thereafter producing output frequencies f o +f/2, f o -f/2, 2f o , 2f o +f, 2f o -f, f, and a DC component in response thereto; a linear, difference-frequency filtering means for receiving said output frequencies from said test transducer and producing as the output thereof only difference-frequency f; and display means, connected to said difference-frequency filtering means and said frequency generating means, for receiving said difference-frequency f from said difference-frequency filtering means and said synchronizing pulse from said frequency generating means, and displaying said difference-frequency f thereon thus permitting observation and measurement of signal characteristics.
Claim 3
Dependent Claim
127 words
An apparatus for detecting defects in transducers under test according to claim 1 wherein said frequency generating means further comprises: a high frequency oscillator for producing a high frequency carrier signal at frequency f o ; a low frequency oscillator for producing a pulsed, low frequency, half-difference-frequency signal, at frequency f/2 and said synchronizing pulse; a double balanced modulator, connected to said high frequency oscillator and said low frequency oscillator, for receiving and combining said high frequency carrier signal at f o and said low frequency, half-difference-frequency signal at f/2 so as to produce said dual-frequency signal at f o +f/2 and f o -f/2; and a power amplifier, connected to said double balanced modulator for receiving and amplifying said dual-frequency signal from said double balanced modulator.
Claim 4
Dependent Claim
127 words
An apparatus for detecting defects in transducers under test according to claim 2 wherein said linear difference-frequency filtering means further comprises: a passive linear low-pass filter, connected to said test transducer, for receiving said test transducer output frequencies and transmitting only said difference-frequency f and said DC component as the output thereof; a linear preamplifier, connected to said low-pass filter, for receiving said low-pass filter output and boosting the levels of said difference-frequency f and said DC component; a linear bandpass filter, connected to said preamplifier, for receiving said difference-frequency f and said DC component from said preamplifier and transmitting only said difference-frequency f as the output thereof; and a linear post-amplifier, connected to said bandpass filter for receiving said difference-frequency f and boosting the level thereof.
Claim 5
Dependent Claim
21 words
An apparatus for detecting defects in transducers under test according to claim 3 wherein said display means further comprises an oscilloscope.
Claim 6
Independent Claim
133 words
A method for detecting defects in transducers under test, comprising the steps of: generating a synchronizing pulse and a dual-frequency signal at frequencies f o +f/2 and f o -f/2, where f o >>f/2; projecting said dual-frequency signal into a water medium using a high power projector; receiving said projected dual-frequency signal at said test transducer which is positioned in close proximity to said high power projector, said test transducer producing output frequencies f o +f/2, f o -f/2, 2f o , 2f o +f, 2f o -f, f and a DC component from said dual-frequency signal; filtering said test transducer output frequencies in such a way as to produce only difference-frequency signal f therefrom; and displaying said difference-frequency signal f upon receipt of said synchronizing pulse to permit measurement of signal characteristics.
Claim 7
Independent Claim
133 words
A method for detecting defects in transducers under test, comprising the steps of: generating a synchronizing pulse and a dual-frequency signal at frequencies f o +f/2 and f o -f/2, where f o >>f/2; projecting said dual-frequency signal into a water medium using a high power projector; receiving said projected dual-frequency signal at said test transducer which is positioned in close proximity to said high power projector, said test transducer producing output frequencies f o +f/2, f o -f/2, 2f o , 2f o +f, 2f o -f, f and a DC component from said dual-frequency signal; filtering said test transducer output frequencies in such a way as to produce only difference-frequency signal f therefrom; and displaying said difference-frequency signal f upon receipt of said synchronizing pulse to permit measurement of signal characteristics.
Claim 8
Dependent Claim
88 words
A method for detecting defects in transducers under test according to claim 5 wherein said generating step further comprises: producing a high frequency carrier signal at frequency f o ; producing a pulsed, low frequency, half-difference-frequency signal, at frequency f/2 and said synchronizing pulse; combining said high frequency carrier signal f o and said low frequency, half-difference-frequency signal at f/2 in such a way as to produce said dual-frequency signal at f o +f/2 and f o -f/2; and amplifying said dual-frequency signal to permit said projecting thereof.
Claim 9
Dependent Claim
89 words
A method for detecting defects in transducers under test according to claim 6 wherein said filtering step further comprises: filtering said test transducer output frequencies to remove high frequency f o components such that only said difference-frequency f and said DC component remain; amplifying said filtered output to boost the levels of said difference-frequency f and said DC component; filtering said difference-frequency f and said DC component to remove said DC component such that only said difference-frequency f remains; and amplifying said difference-frequency f to boost the level thereof.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-05-01 | 1987-10-31 | 1988-05-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-05-01 | 1991-10-31 | 1992-05-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-05-01 | 1995-10-31 | 1996-05-01 | $7700.00 | Window Closed / Lapsed |