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I was reading a manual of an oscilloscope, and I noticed in working environment section it mentions something about altitude. What does altitude have to do with oscilloscopes?

It says operating less than 3km and non operating less than 15km

The oscilloscope is Rigol DS1000Z.

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  • \$\begingroup\$ The manual of my ancient PM3212 says the same thing. I assumed it has something to do with the CRT being vacuum. Your oscilloscope however has no CRT, so I need to abandon that idea. \$\endgroup\$ – Bart Mar 6 at 10:02
  • \$\begingroup\$ @Bart CRTs work well in external underpressure, usually. It reducess the stress on them, theoretically. \$\endgroup\$ – Marcus Müller Mar 6 at 10:03
  • \$\begingroup\$ @MarcusMüller maybe it has to do with more ionizing radiation at altitude? \$\endgroup\$ – Bart Mar 6 at 10:04
  • \$\begingroup\$ @Bart I'd guess they'd specify that, then. \$\endgroup\$ – Marcus Müller Mar 6 at 10:08
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    \$\begingroup\$ Air density also matters; above 3000 metres the air density is low enough to affect convection cooling significantly (so the thermal resistance is effectively higher for parts leading to higher operating temperatures). There is also fan operation to consider (it has to work harder in low pressure). \$\endgroup\$ – Peter Smith Mar 6 at 10:18
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In order to comply with some safety regulations and standards, especially related to creepage and clearance, the insulation characteristic of the air is considered. At high altitudes, the air's insulating characteristic changes, and so does the the electronics' behaviour. In the case of oscillocopes, it is probably even more sensitive due to its high speed electronics / bandwidth and the possibility of reducing the isolation between some traces or components (source of noise due to coupling).

More to that in here

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  • \$\begingroup\$ Specifically, I would wager that input isolation is the culprit. Since for safety warning we only care about the high voltage traces. Typical oscope has 300VAC input rating for the probe and this can demand a lot of the front end. The creepage change can be significant, from spacing ~1mm to >3mm at high altitude for 300V isolation. The other place high voltage is seen is in the power supply circuit \$\endgroup\$ – crasic Mar 8 at 2:10
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Your oscilloscope probably depends on proper convection to eliminate heat from the electronics. As the air gets thinner it is less able to remove heat from the components, so there might be a possibility of overheating at high altitudes.

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The spec sheet gives a transient voltage rating of 1000V. With a tight circuit layout, necessary for fast response, that may arc at high altitude.

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It is essentially certifying it (or not) for use in an aircraft for test purposes. This assumes it's used in an unpressurised cabin. For a pressurised cabin you can go with the effective altitude for comparison with the specification limit.

You should also beware of unusual atmospheric gasses at higher altitudes, often caused by the effects of the bright sunshine, e.g. ozone O3.

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