UhClem
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- Feb 6, 2009
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How do you propose I fix this? I can't put a capacitor on it since a capacitor from ground to ground really doesn't do much... The ground voltage changes all the time anyway. Mount your altimeter on a sled? You just changed the ground voltage with all the static charge on the sled.
The problem isn't caused by the absolute ground voltage changing but that the difference between Vcc and ground changes. The regulator is almost certainly of the series pass design which means that it cannot sink current. So if something should cause the difference between its output and ground to rise, it can do nothing to stop it.
Filtering (ferrite beads and capacitors) are the only way to prevent RF entering via your external connections from causing trouble. You could ignore it and hope that there is never a source of RF around strong enough to cause trouble. That works for most altimeters most of the time.
The BMP280 may help as it has an internal regulator.
Decoupling capacitors are not used to keep power supply noise out of the parts but to provide a local low impedance reservoir for when the current demanded by that part changes suddenly.Everything sensitive has a decoupling capacitor attached to it.