US3798539A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Pulse eddy current testing apparatus using pulses having a 25% duty cycle with gating at pulse edges
Assignee: MAGNETIC ANALYSIS CORP US
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Filing: 1973-02-15
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Granted: 1974-03-19
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Expires: 1993-02-15
Abstract
Abstract Pulses having a pulse width equal to one-quarter wavelength at a multiple (including 1) of the fundamental frequency of the pulses are applied to the test coil assembly of a pulse eddy current testing apparatus, and the output signals are supplied to an amplifier tuned to said multiple of the fundamental frequency. The output of the amplifier is supplied to a pair of phasesensitive detectors which are gated at the leading and trailing edges of the applied pulses to produce quadrature signal components. These components are utilized to produce indications of defects or flaws in the object under test. The test coil assembly is advantageously designed to produce an approximately null output in the absence of defects or flaws. The pulses may have a 25 percent duty cycle with the amplifier tuned to the PRF thereof.
Inventors
- 👤 R Brooks
- 👤 P Bebick
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 10:35
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/72; G01N27/82; G01N27/90; G01N27/9046
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
158 words
Pulse eddy current testing apparatus which comprises a. a pulse generator for producing regularly recurring pulses having a pulse width equal to one-quarter wavelength at a multiple (including 1) of the fundamental frequency of said pulses, b. test coil means supplied with said pulses for inducing eddy currents in an object under test and producing output signals varying with defects or flaws in the object, c. an amplifier tuned to substantially said multiple of the fundamental frequency of the pulses supplied to said test coil means and supplied with the output signals thereof, d. means for producing gate pulses at the leading and trailing edges of said pulses, e. a pair of phase-sensitive detectors supplied with said gate pulses and with the output of said tuned amplifier for producing quadrature signal components thereof, f. and means for utilizing the signal components from said phase-sensitive detectors to produce indications of said defects or flaws in the object under test.
Claim 2
Dependent Claim
158 words
Pulse eddy current testing apparatus which comprises a. a pulse generator for producing regularly recurring pulses having a pulse width equal to one-quarter wavelength at a multiple (including 1) of the fundamental frequency of said pulses, b. test coil means supplied with said pulses for inducing eddy currents in an object under test and producing output signals varying with defects or flaws in the object, c. an amplifier tuned to substantially said multiple of the fundamental frequency of the pulses supplied to said test coil means and supplied with the output signals thereof, d. means for producing gate pulses at the leading and trailing edges of said pulses, e. a pair of phase-sensitive detectors supplied with said gate pulses and with the output of said tuned amplifier for producing quadrature signal components thereof, f. and means for utilizing the signal components from said phase-sensitive detectors to produce indications of said defects or flaws in the object under test.
Claim 3
Dependent Claim
31 words
Apparatus in accordance with claim 1 in which said pulses supplied to the test coil means have a 25 percent duty cycle and said amplifier is tuned to the PRF thereof.
Claim 4
Dependent Claim
36 words
Apparatus in accordance with claim 1 in which said test coil means includes output coils connected to produce approximately a null output to said tuned amplifier in the absence of defects or flaws in said object.
Claim 5
Dependent Claim
41 words
Apparatus in accordance with claim 1 in which said means for producing gate pulses includes a pair of differentiating circuits supplied with said pulses from the pulse generator and designed and adapted to differentiate the leading and trailing edges thereof, respectively.
Claim 6
Dependent Claim
139 words
Pulse eddy current testing apparatus whIch comprises a. a pulse generator for producing pulses having a 25 percent duty cycle, b. test coil means supplied with said pulses for inducing eddy currents in an object under test and producing output signals varying with defects or flaws in the object, c. an amplifier tuned to the PRF of the pulses supplied to the test coil means and supplied with the output signals thereof, d. means for producing gate pulses at the leading and trailing edges of said 25 percent duty cycle pulses, e. a pair of phase-sensitive detectors supplied with said gate pulses and the output of said tuned amplifier for producing quadrature-signal components thereof, f. and means for utilizing the signal components from said phase-sensitive detectors to produce indications of said defects of flaws in the object under test.
Claim 7
Dependent Claim
139 words
Pulse eddy current testing apparatus whIch comprises a. a pulse generator for producing pulses having a 25 percent duty cycle, b. test coil means supplied with said pulses for inducing eddy currents in an object under test and producing output signals varying with defects or flaws in the object, c. an amplifier tuned to the PRF of the pulses supplied to the test coil means and supplied with the output signals thereof, d. means for producing gate pulses at the leading and trailing edges of said 25 percent duty cycle pulses, e. a pair of phase-sensitive detectors supplied with said gate pulses and the output of said tuned amplifier for producing quadrature-signal components thereof, f. and means for utilizing the signal components from said phase-sensitive detectors to produce indications of said defects of flaws in the object under test.
Claim 8
Dependent Claim
36 words
Apparatus in accordance with claim 5 in which said test coil means includes output coils connected to produce approximately a null output to said tuned amplifier in the absence of defects or flaws in said object.
Claim 9
Dependent Claim
44 words
Apparatus in accordance with claim 6 in which said means for producing gate pulses includes a pair of differentiating circuits supplied with pulses corresponding to said 25 percent duty cycle pulses and designed and adapted to differentiate the leading and trailing edges thereof, respectively.
Claim 10
Dependent Claim
75 words
Apparatus in accordance with claim 5 in which said means for producing gate pulses includes a differential amplifier supplied with pulses corresponding to said 25 percent duty cycle pulses and yielding corresponding inverted and non-inverted pulse outputs, and a pair of differentiating circuits supplied with said pulse outputs respectively, said differentiating circuits being designed and adapted to produce gate pulses of the same polarity at respective leading and trailing edges of the pulses supplied thereto.
Claim 11
Dependent Claim
36 words
Apparatus in accordance with claim 8 in which said test coil means includes output coils connected to produce approximately a null output to said tuned amplifier in the absence of defects or flaws in said object.
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) | 1977-03-18 | 1977-09-17 | 1978-03-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-18 | 1981-09-17 | 1982-03-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-18 | 1985-09-17 | 1986-03-19 | $7700.00 | Window Closed / Lapsed |