The microprocessor that had one damaged A/D input finally failed yesterday due to a lightning strike a month ago. All the A/D inputs were reading maximum values. Refrigerator shut down because it thought the battery was at 19V. Program also read voltage from a 2.5V reference. Reading a correct value indicated that the 5V supply was stable. Program sections checked for this OK flag to know the A/D values could be trusted. I’m moving to a more distributed system so program changes can be made without fear that an error will shut down the fridge for an extended time.
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