thommen altimeter instructions for 1040x

A normal one will have a temperature diaphragm as well as a barometric diaphragm pushing springs/gears around. If you ever get a chance and are curious, you may want to open up an aircraft grade altimeter sometime. They will have gears in there as well on dial gauges with multiple dials as the Thommen has or multiple coil springs. They are all either straight diaphragm no spring less than 360 degrees rotation and if they do go past their maximum allowed rotation they break, or diaphragm pushing a coil spring for multiple revolutions, or diaphragm pushing a spring turning a gear. If it was JUST a diaphragm you would have to have a paddle gear motion from said diaphram liquid moving the dial, which is absurd as this would require a perfect seal on the gear axle as well as the interface between gear and the liquid that would not allow the air pocket required to be around said gear. How all aircraft altitude meters have been made for the last oh, 70 years now, have been via a coil spring/gears. Whichever method you chose to correlate a diaphragms motion into a dial is up to you. I am thinking you are thinking extension springs when I said spring. You have to have a diaphragm pushing a coil torsion spring to move said dial around the dial multiple times. Won't tell you much other than if the Thommen was manufactured correctly with the correct spring/diaphragm specs.ĭon't know how a dial altimetere is built Now: If you are going to JUST check barometric pressure then sure, pull up KOMO weather,, SEATAC and get realtime updates and track the barometric pressure and compare to your hearts content from different stations, say at Paradise and SEATAC. This is especially critical at high altitude airports with a shadded zone with a TOP boundary temperature gradient and a Bottom boundary temperature gradient along with the equation present so the poor SOB trying to fly the plane can calculate the true Altitude that he is trying to lift off in! Crashing really sucks. That is why all planes have an Altitude Density LOAD CAPACITY CHART. Ones TRUE equivalent altitude is derived from an equation based on the barometric pressure and temperature. Your 2nd post makes the same mistake.Ĭhecking altitude won't help you much as your true elevation will be HIGHLY dependent on the temperature away from STP along with pressure away from STP. Good luck on arriving at a barometric station under STP. Barometric pressure is only true elevation under STP conditions. Your post made it sound like you were going to hike to a certain altitude and check the altitude. Your ego is about to get smacked: It would have been fine if you had even bothered to do a wikipedia search before your knee jerk response of, 'I AM RIGHT!'. Your Thommen is not a fake and is just fine. Its not like the Thommen is an aircraft grade altimeter creating a larger selling audience.ĭial Guages, especially pressure gauges, either work, need an offset added(calibration), or break. Besides the numbers they could actually sell is abysmally low. No one will build a fake Thommen and try passing it off as a real one. Otherwise if you are only really reading 1 dial, you are(elevation not pressure), then a bent needle makes no difference as long as the built in calibration dial can compensate. It will introduce an offset error if 2 hands are present on said guage.

It does not have a bimetallic temperature compensation diaphram like higher end altimeters do as far as I know.Ī bent needle can be caused because it was dropped. I believe the Thommen will have a metalic diaphram and therefore will be the last thing to fail. A failed diaphram is possible, but then again, the gauge won't work. The calibration dial simply moves the spring stop a very small distance. Springs on the other hand retain their spring constant till they fatigue and break and therefore your gauge will not move at all. IE the needle will have a higher stiction. This 'problem' is easily taken care of by tapping the gauge obtaining the correct value. Pretty much the only mechanical error that will ever be introduced is in the needle bearing wearing out. So, unless you happen to know the exact temperature at which Thommen first calibrated their altimeters.

That ol' Temperature to the fourth power in the equation dominates all. Your elevation error is more dependent on temperature than anything else for error.

Thommen altimeter instructions for 1040x