US3786347A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for generating stable driving pulses for an eddy current test system
Assignee: MAGNETIC ANALYSIS CORP US
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Filing: 1972-12-21
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Granted: 1974-01-15
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Expires: 1992-12-21
Abstract
Abstract Pulses for energizing an eddy current test coil assembly are produced by apparatus comprising a sine wave oscillator feeding a square wave generator, and a pulse generator and pulse hold-off circuit wbich produces output pulses corresponding to regularly recurring non-sequential excursions of one polarity of the square wave. The hold-off circuit includes a flip-flop which is reset at the trailing edges of the output pulses, and set at edges of the square wave next preceding the output pulses. The output pulses drive a test coil assembly for inducing eddy currents in an object under test and producing output signals varying with defects or flaws therein. The output signals pass to an amplifier tuned to the PRF of the pulses and then to a pair of gated phasesensitive detectors Quadrature gates are developed from the holdoff circuit and a second similar circuit at times precisely related to the output pulses.
Inventors
- 👤 S Mansson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 18:14
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/72; G01N27/82; G01N27/90; G01N27/9046; H; H03; H03K; H03K5/00; H03K5/01; H03K5/04
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
215 words
Pulse eddy current testing apparatus which comprises a. a sine wave oscillator, b. a square wave generator supplied with the sine wave from said oscillator for producing a square wave therefrom having the same frequency, c. a pulse generator supplied with said square wave and a pulse hold-off circuit cooperating therewith for producing output pulses corresponding to regularly recurring non-sequential excursions of one polarity of the square wave supplied to the pulse generator, d. said pulse hold-off circuit including flip-flop means having set and reset states, e. control means responsive to the set and reset states of said flip-flop means for respectively allowing and preventing the production of output pulses by said pulse generator, f. resetting means responsive to the trailing edge of an output pulse from said pulse generator for resetting said flip-flop means, g. setting means responsive to a square wave from said square wave generator for setting said flip-flop means at or after the trailing edges of excursions of said one polarity next preceding said non-sequential excursions but prior to said nonsequential excursions, h. test coil means for inducing eddy currents in an object under test and producing output signals varying with defects or flaws in the object, i. and means for utilizing said output pulses to drive said test coil means.
Claim 2
Dependent Claim
215 words
Pulse eddy current testing apparatus which comprises a. a sine wave oscillator, b. a square wave generator supplied with the sine wave from said oscillator for producing a square wave therefrom having the same frequency, c. a pulse generator supplied with said square wave and a pulse hold-off circuit cooperating therewith for producing output pulses corresponding to regularly recurring non-sequential excursions of one polarity of the square wave supplied to the pulse generator, d. said pulse hold-off circuit including flip-flop means having set and reset states, e. control means responsive to the set and reset states of said flip-flop means for respectively allowing and preventing the production of output pulses by said pulse generator, f. resetting means responsive to the trailing edge of an output pulse from said pulse generator for resetting said flip-flop means, g. setting means responsive to a square wave from said square wave generator for setting said flip-flop means at or after the trailing edges of excursions of said one polarity next preceding said non-sequential excursions but prior to said nonsequential excursions, h. test coil means for inducing eddy currents in an object under test and producing output signals varying with defects or flaws in the object, i. and means for utilizing said output pulses to drive said test coil means.
Claim 3
Dependent Claim
66 words
Apparatus in accordance with claim 1 in which said setting means sets said flip-flop means at or after the trailing edges of alternate excursions of said one polarity of the square wave supplied to said pulse generator but prior to the respective next excursions thereof, whereby output pulses of 25 percent duty cycle and a PRF one-half the frequency of said sine wave oscillator are produced.
Claim 4
Dependent Claim
31 words
AppAratus in accordance with claim 1 in which said control means includes short-circuiting means responsive to the reset state of said flip-flop means to short-circuit the input of said pulse generator.
Claim 5
Dependent Claim
53 words
Apparatus in accordance with claim 1 in which said setting means includes means for differentiating a square wave from said square wave generator to produce setting trigger pulses at edges of the square wave next preceding said output pulses respectively, and means for utilizing said setting trigger pulses to set said flip-flop means.
Claim 6
Dependent Claim
29 words
Apparatus in accordance with claim 4 in which the square wave supplied to said setting means is inverse with respect to the square wave supplied to said pulse generator.
Claim 7
Dependent Claim
75 words
Apparatus in accordance with claim 5 in which said resetting means includes means for differentiating the output pulses of said pulse generator to produce resetting trigger pulses at the trailing edges thereof, and short-circuiting means responsive to said resetting trigger pulses for resetting said flip-flop means, said short-circuiting means having a high resistance in the non-short-circuiting condition thereof and forming part of the means for differentiating the square wave to produce said setting trigger pulses.
Claim 8
Dependent Claim
60 words
Apparatus in accordance with claim 1 including a tuned amplifier supplied with said output signals of the test coil means, said amplifier being tuned to a frequency substantially one-half the frequency of said sine wave oscillator, and gated phase-sensitive detector means supplied with the output of said amplifier for producing signals corresponding to said defects or flaws in the object.
Claim 9
Dependent Claim
61 words
Apparatus in accordance with claim 2 including a tuned amplifier supplied with said output signals of the test coil means, said amplifier being tuned to substantially a multiple (including 1) of the PRF of said output pulses, and gated phase-sensitive detector means supplied with the output of said amplifier for producing signals corresponding to said defects or flaws in the object.
Claim 10
Dependent Claim
20 words
Apparatus in accordance with claim 8 in which said amplifier is tuned to substantially the PRF of said output pulses.
Claim 11
Dependent Claim
190 words
Apparatus in accordance with claim 9 in which said resetting means includes means for differentiating the output pulses of said pulse generator to produce resetting pulses at the trailing edges thereof for resetting the flip-flop means, said flip-flop means is set at the trailing edges of alternate excursions of said one polarity of the square wave supplied to said pulse generator, and said gated phase sensitive detector means includes a pair of gated phase-sensitive detectors, and including means for generating early and late gate pulses for respective detectors comprising a. a differentiating means responsive to the setting of said flip-flop means for producing said late gate pulses, b. second flip-flop means having set and reset states, c. means for utilizing said resetting trigger pulses to reset said second flip-flop means, d. means for differentiating a square wave from said square wave generator to produce setting trigger pulses at edges thereof next following said output pulses respectively, e. means for utilizing the last-mentioned setting trigger pulses to set said second flip-flop means, f. and differentiating means responsive to the setting of said second flip-flop means for producing said early gate pulses.
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) | 1977-01-14 | 1977-07-16 | 1978-01-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-14 | 1981-07-16 | 1982-01-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-14 | 1985-07-16 | 1986-01-15 | $7700.00 | Window Closed / Lapsed |