Isolation Resolution
Fault isolation in automated test systems represents the process of locating the exact failing component on a circuit assembly. When multiple components share a common node, a diagnostic ambiguity group designates the collection of suspect parts that cannot be further isolated by the test program. For instance, if a pull-up resistor and the integrated circuit pin it connects to both fail to drive high, the tester identifies them together.
This grouped reporting represents the physical limitation of the probe access and the circuit layout.
Tester Output
Diagnostic printouts list all potential culprits when a test step fails to pinpoint a single component. System operators use this diagnostic ambiguity group to guide manual inspection and measurement of the identified components. Designers minimize the size of these groups by adding test points to specific nodes during the schematic design phase.
Production Impact
Large groups of suspected parts increase the time and labor required for rework since technicians must manually probe each listed component. The diagnostic ambiguity group remains a primary metric for evaluating the diagnostic resolution of in-circuit and functional test programs. Ensuring that most groups contain only one or two components improves the throughput of the repair station.
