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US4774455A Expired / Lapsed US ⏱️ 0.0 years remaining

Method for automatic guard selection in automatic test equipment

Assignee: Schlumberger Technologies Ltd
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Filing: 1986-03-14
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Granted: 1988-09-27
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Expires: 2006-03-14
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Abstract

Abstract During the testing of circuit boards with Automatic Test Equipment in some circuit configurations the performance of a component may not be as expected even though it is sound due to the influence of surrounding components. In such a situation guards may be placed, that is further signals via probes contacting nodes other than those to which the component is connected, so that such disruption may be minimized. A method for defining guards during the operation of automatic test equipment so that a selected component of a circuit may be tested includes establishing a measurement of the selected component in a known to be good circuit of the type to be tested. A circuit node associated with the selected component is identified and a guard is applied to the node. A second measurement is established with the selected guard in place. If the guard results in an improvement, it is retained during subsequent automatic testing.

Inventors

  • 👤 Lewis Williams

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-29 14:29
CPC Classifications
G; G01; G01R; G01R31/00; G01R31/28; G01R31/2801; G01R31/281; G01R31/2813

Claims Analysis

Total Claims: 10
Claim 1
Independent Claim 92 words
A method for defining guards during the operation of automatic test equipment so that a selected component of a suspect circuit may be tested including the steps of: establishing a first measurement of the selected component in a known to be good circuit of the type to be tested, identifying a circuit node associated with the selected component, applying a guard to the node, establishing a second measurement with the guard in place, and, should the guard result in an improvement, retaining that guard during subsequent automatic testing of the suspect circuit.
Claim 2
Independent Claim 92 words
A method for defining guards during the operation of automatic test equipment so that a selected component of a suspect circuit may be tested including the steps of: establishing a first measurement of the selected component in a known to be good circuit of the type to be tested, identifying a circuit node associated with the selected component, applying a guard to the node, establishing a second measurement with the guard in place, and, should the guard result in an improvement, retaining that guard during subsequent automatic testing of the suspect circuit.
Claim 3
Dependent Claim 29 words
A method for defining guards as claimed in claim 1, wherein all circuit nodes associated with the selected component are identified and a guard applied to each in turn.
Claim 4
Dependent Claim 18 words
A method for defining guards as claimed in claim 1, wherein a limited number of guards are retained.
Claim 5
Dependent Claim 20 words
A method for defining guards as claimed in claim 1, wherein guards are applied in combination and further measurements performed.
Claim 6
Dependent Claim 28 words
A method for defining guards as claimed in claim 4, wherein improvement is assessed with respect to an initial reference being an unguarded or a topographically guarded measurement.
Claim 7
Dependent Claim 36 words
A method for defining guards as claimed in claim 1 wherein a guard is selected for a component for which a first measurement produces a result which is inconsistent with that expected from a sound component.
Claim 8
Dependent Claim 36 words
A method for defining guards as claimed in claim 1 wherein a second measurement is established with a plurality of guards in place and any improvement is degraded as a function of the number of guards.
Claim 9
Dependent Claim 32 words
A method for defining guards as claimed in claim 1, wherein a component measurement is established by injecting a signal at a first component node and measuring response at a second node.
Claim 10
Dependent Claim 40 words
A method for defining guards as claimed in claim 1, wherein the measurement is re-established by injecting a signal at the second node and measurement at the first node and the guarding re-applied so that the best combination is selected.

References Cited (Backward Citations)

US3931506A Cited
US4070565A Cited
US4555783A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1991-09-27 1992-03-28 1992-09-27 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1995-09-27 1996-03-28 1996-09-27 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1999-09-27 2000-03-28 2000-09-27 $7700.00 Window Closed / Lapsed

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