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The higher the
altitude, the lower the atmospheric pressure
gets. To simulate this effect vacuum chambers are
employed. Testing may be a single test to see at
what maximum altitude the device will fail.
Altitude cycling is also employed to see the
repeated effects of pressure changes. This is
particularly important for components that might
experience multiple take-offs and landings.
Finally, note that the rate of change in pressure
may impact certain components.
A first step should be
to investigate what components are vulnerable to
this effect and review vendor testing to
understand what testing has been done by others,
but be careful to note the actual conditions under
which those results were obtained. A judgement
call must be made at this point as to whether
additional testing is warranted for the full
design. This should be based on the component
test data available, the relationship of test
conditions to the projected operating environment
(or worst case) for the design, and the potential
consequences of the design failing in this manner.
A final note is that
altitude testing is sometimes combined with other
stress environments. Temperature and
humidity are common. Power cycling is also employed
in some situations to further stress the device.
The translation between vacuum pressure and
altitude is given for information below. |
