You've almost certainly seen a pressure gauge somewhere: on an air compressor, a steam boiler or perhaps an automotive vacuum gauge. Have you thought much about how that gauge works? Magic? Elves? We'll rip one open to find out.
Anyone who has been reading my posts will have surmised that I like clever mechanisms. The Bourdon tube, which is the source of the pressure gauge's magic, certainly qualifies.


Simple and clever. Almost like magic.
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I saw a great "How It's Made" episode on these. My only concern was metal fatigue generating errors over time as copper tends to stiffen significantly when it is bent.
@animemaster That's a great point. While these tubes only move very small amounts in operation, slight work hardening will still occur over time. That probably explains at least part of why these gauges need to be calibrated periodically. The one photographed here was last calibrated sometime around 1991.