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Why not -50 to 90?

How was the temperature range of -40 to 85c chosen to become the industrial standard? (Some products may have a different operating temperature range, but for the majority, the chosen spec is 85 to -40)

Is there any scientific paper that shows this is a good range to qualify component?

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Why not -35 to 75 ? Probably because that range covers the temperatures most often encountered by most equipment produced for use in society - excluding, of course, equipment produced for exceptional locations...

Care has to be taken that items should be used within their working range of temperature : something so simple as a rubber O ring can fail if used outside or below its defined working temperature range.

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  • \$\begingroup\$ O-Ring failure. \$\endgroup\$ – JRE Jan 14 '19 at 9:01
  • \$\begingroup\$ @JRE Sadly, best example ever - I hope every engineer or designer learns from that so nothing like it happens again. \$\endgroup\$ – Solar Mike Jan 14 '19 at 9:04
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    \$\begingroup\$ As I understand it, the engineers had figured it out and recommended against starting on that day. Further up decided to ignore the warning. \$\endgroup\$ – JRE Jan 14 '19 at 9:07
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    \$\begingroup\$ @JRE Feinmann's book gave a good explanation... Apparently he was not going to accept the position on the enquiry - but his wife said "you will be the only one shoving your nose where they don't want you to look"... and his personal notes show he "tripped" over the temperature issue on day 2 or 3 (roughly from memory)... \$\endgroup\$ – Solar Mike Jan 14 '19 at 9:10
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    \$\begingroup\$ The woman on the investigation has given notes from inside NASA. She passed them to Richard Feynmann, and signaled him when to bring up the results of his "O-ring in ice water" experiment to the investigating board. Per an article in Popular Mechanics a few years ago. \$\endgroup\$ – analogsystemsrf Jan 14 '19 at 14:42

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