Sunday, October 07, 2007

Checking altimeters

I am playing a bit with the instruments... again. A few years ago I bought this vacuum chamber and a pump to seal some electronic parts, now there is a new use for it.
It seems the altimeters are still working good, despite my unqualified 'servicing'. Until 20'000 feet they go perfectly synchronous, above 25'000 they have a little difference of 300 ft. But I don't know to what altitude they are calibrated, so I assume that's more or less ok. They won't be used in an aircraft anyway.

By the way... did you know that on 20'000 ft there is only half the pressure than on the ground? It's a vacuum of -0.5 Bar (0.5 kgf per cm2... or 5N per cm2... or 500 hpa.... or 14.76 inches of Hg)
And you have a 80% vacuum at 40'000ft.

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