Take an old controller PC and a new one. Feed them the same inputs, and check you get the same outputs. You don't even need to hook them to a real scanner. You had a test suite, right?
Divide the cost of the retesting between your customers - Just add it to their maintenance contracts. It's cheaper for them than buying a new scanner or killing someone.
I've been arguing this for years, and no-one has ever given me a reasonable explanation of why I might be wrong. Maybe this time
Biting the hand that feeds IT
