Re: Garmin altitude problems

On 8/10/2024 8:38 PM, Jeff Liebermann wrote:

 As I understand it, all aviation barometric altimeters are temperature
compensated.  I would think the aviation temperature compensation for
air density method is somewhat similar to a marine barometer:
<https://www.faa.gov/air_traffic/publications/atpubs/aip_html/part2_enr_section_1.8.html>
I couldn't find anything that shows how the various gears work and
where the bi-metallic temperature compensator is located (because of
numerous interruptions today).

I just opened up the wall mounted aneroid barometer here in my study, an antique I inherited. It's an extremely simple lever mechanism, no gears involved. The capsule pushes up or down on a long thin lever arm. The vertical motion of the lever's end is converted to a horizontal motion of a tall thin post, which anchors the end of the smallest roller-style chain I've ever seen, maybe 0.050" pitch. That wraps around the needle's pivot shaft.  Here's a photo:
https://www.flickr.com/photos/16972296@N08/53916400376/in/dateposted-public/   (Sorry, the "tall thin post" is in shadow.)
The left end of the lever system is not a pivot point, but instead is a rather wide brass stamping. I'd think that part could be made bimetallic to provide temperature compensation.
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- Frank Krygowski