How would you validate a safety interlock when residue and thermal distortion can change the same position signal?

A closed-position switch can look reliable on a clean, room-temperature assembly while becoming ambiguous after thermal growth, residue buildup, latch wear or panel tolerance stack-up. The dangerous failure is not only a missed open state; an interlock can also nuisance-trip often enough that operators learn to defeat or ignore it.

I would separate the mechanical state from the electrical indication, define representative clean and contaminated conditions, and cycle the assembly through matched thermal histories. Evidence could include independent gap measurement, latch force, switch transition position, contact bounce and fault-injection cases for stuck or drifting signals. Acceptance should cover both unsafe false-closed behavior and excessive false-open behavior.

What test matrix best reveals common-cause errors between the physical closure and the sensor that reports it without making the fixture more repeatable than the product?

Disclosure: I work with Libergeon on H350 development. H350 remains in development and prototype validation; it is not for sale, has no announced price, and accepts no preorders. No product link.