The use of cutoffs when used allows a tremendous number of options to the Analyst. Just as test weighting can help the Analyst to control the Isolation sequence so can the use of Cutoffs. Its primary use is to reduce the diagnostic time by limiting the algorithms to a group of 1 up to N (Count) setable limits and determine action taken when the limiting condition is met. It is particularly good for multiple fault algorithms where refinement is utilized. Cutoffs are used to restrict the duration of testing in an isolation path. The diagnostic sequence and isolation test resources are only searched when the cutoff either involves tests used in a particular way (e.g., refinement tests) or when the cutoff is explicitly related to the test group in the algorithm. The time spent checking depth-of-isolation can be reduced substantially by using Cutoffs. When fault isolation is calculated for selected (as opposed to all) detection tests, eXpress correctly uses any changes made to the default weightings and cutoffs for the selected algorithm.
When cutoffs are used to restrict the length of an isolation path, the diagnostic sequence and isolation test resources are only searched when the cutoff either involves tests used in a particular way (e.g., refinement tests) or when the cutoff is explicitly related to the test group in the algorithm. As a result, the time spent checking depth-of-isolation cutoffs has been reduced substantially.
Matrix of Limiting Cutoff Parameters Possibilities
Entity/Domain
Full diagnostic Path
Isolation Path
Candiate Tests
Number of Tests (default)
X (default)
Number of Items
Number of Functions
Replacement Cost
Replacement Time
Test Cost
Test Time
Failure Rate
Failure Probability
Modifier 1
Detection
Isolation
Refinement
Explicid Inference
None
Test Set
Test Type
Test Usage (default)
X (default)
Test Outcome
Modifier 2
Pass
Fail
Found
No Found
None
Test Set
Test Type
Test Usage
Test Outcome (default)
X (default)
Condition Count defaulted to 3 for this example
Action to be taken when conditions is met
None
Terminate to current Isolation Sequence
Select no more Isolation Tests from this Grouping (default)
Use no more Refinement test in current sequence
Use no more Refinement test in current Grouping
Here we see:
Number of Tests in the Isolation Paths limited to a setable Count (Here the condition is met when the number of tests within the Isolation Path (not refinement) reaches 3
Test usage limited for use in Refinement testing to a setable Count (Here Condition is met with 3 (Count) alternate paths (refinement) attempts to refine to smaller ambiguity set)
Test Outcome limits the use of Ignore in Sequence and Ignore in Group to 3 for multiple fault algorithms. Isolation Algorithms
For Test Outcome cutoffs, the options to “Ignore in Sequence” and “Ignore in Group” are available when “Test Outcome” is selected as one of the two modifiers (these options still do not appear, however, when “Test Outcome” is the only modifier).
