Prevent Persistent Station State from Leaking Into the Next PCB Test

A test station often retains useful information between runs, including resource configuration or operator preferences. Trouble begins when unit-specific values remain in the same persistent space. The next board can inherit a variant, bypass flag, or cached result without anyone deliberately selecting it.

NI’s station-global persistence guidance explains that station-global values can be saved and retained between executions. Persistence therefore needs a deliberate ownership and reset policy rather than an assumption that every run starts empty.

Classify variables by lifetime

Identify values that belong to the station, the current session, the fixture socket, the unit, and the individual step. Place each value at the narrowest practical scope. Name the owner responsible for initializing it and the event that ends its validity. A board identifier or fitted-option flag should not become station configuration simply because a global variable is convenient to access.

Initialize before making decisions

At the start of an attempt, clear unit-specific status and load the required configuration from its authoritative source. Use an explicit unknown or uninitialized state where that helps distinguish missing information from a legitimate zero, false, or empty value.

Do not depend solely on end-of-run cleanup. A power interruption or application crash may prevent that cleanup from occurring. Start-of-run validation provides a separate opportunity to reject stale information before it influences coverage or acceptance.

Test transitions between unlike units

Run two configurations in alternating order, including a feature-rich variant followed by one without the feature. Introduce an interrupted attempt between them. Inspect which values survive and whether each subsequent board selects the correct tests and limits.

Repeat after restarting the application, because persistence across process restarts can differ from persistence between sequence calls. Document the intended behavior for retained station settings so validation does not mistake an approved retained value for contamination.

Review cached instrument settings separately. A software variable saying that an instrument is configured does not prove the instrument retained that state after reconnection or reset. Reestablish the necessary conditions at the defined boundary.

The result should be a clear lifetime contract for every consequential value. A new board begins with verified configuration and empty result state, while genuinely persistent station information remains controlled and identifiable.