Tissot T Touch Titanium expert Altimeter

ShanE90

Hi, My watch doesn't seem to maintain the correct alt while sitting in the same place for a few days, the altimeter can be at 88m and a few days later 150m without movement, it needs constant calibration which is annoying, is this a normal characteristic of the t touch?

It's titanium which marks very easily, is this something I could polish myself or should I have it done professionally..

Shane.

Wibbs

Well I presume it runs off atmospheric pressure? If so the reading will change because atmospheric pressure does. I expect it would have to be zeroed to a known height to be accurate.

ShanE90

Yes it calculates altitude from the baro reading, it's fairly accurate and I calibrated it at sea level when I got

Wibbs

Yep but barometric pressure varies and varies quite a bit, even over the course of a day so for accuracy you'd have to reset it to sealevel every time you required such accuracy. Bit of a pain but there you go. Pilots have to do it with onboard altimeters(well the old style ones, I suppose the new ones run off GPS). I've a world war two cockpit altimeter from a German JU87 Stuka dive bomber and it has an adjusting knob, so the pilot could readjust/set the zero height every mission. Damned important especially on a dive bomber or you could end up digging a very big hole at very high speed if you got it wrong.

ShanE90

Thanks for the detailed explanation! What I don't get is that when the baro rises and falls and accordingly adjusts the alt how do the alt and baro both end up reading wrong...

During the week the baro read the correct pressure and alt all week then I noticed the baro at 1025 when I knew the pressure was 1010, so I checked the alt and it was incorrect too.

What happens is the baro sets the alt to the incorrect level then the new alt reading effects the baro reading by showing it too high?

Wossack

think the reality is, that at ground level, you need a very accurate barometer to calculate altitude to any degree of accuracy. Difference between sealevel and 1km up is like 125hPa. And thats not accounting for the variation in air pressure due to weather patterns (which can be +/- 30hPa or more ).

Believe all altimeter calculations are made from the single barometer (which calculates the delta between the current, and the original calibrated 'zero', and equates that to an 'height'). Altimeter should have no feedback to the barometer reading, but I could be wrong

Also, when setting your altimeter on your Stuka before take off, make sure you dont zero it to sea level, but to the runways elevation above sea level