Doubt about Suunto 9 Baro altimeter/barometer calibration

johann.fuehrer

@Dimitrios-Kanellopoulos
https://www.zamg.ac.at/cms/de/wetter/wetterwerte-analysen/wien/luftdruck/?mode=geo&druckang=red

It’s Vienna and “Wien Unterlaa” is the station I mentioned …

https://www.zamg.ac.at/cms/de/wetter/wetterwerte-analysen/tawes-verlaufsgraphiken/wien_unterlaa/luftdruck/?mode=geo&druckang=red

johann.fuehrer

@Dimitrios-Kanellopoulos … and yes, it’s seal level pressure. Local pressure is about 993 hPa

You can switch in the pressure chart caption!

@Dimitrios-Kanellopoulos said in Doubt about Suunto 9 Baro altimeter/barometer calibration:

Lets keep an eye on this.

I think that I understood some extra… On my workings days I use a lot the stairs. This results in variations of more than 5m in less than 12 minutes, that result that my watch change to alti-mode. When I have a weather change the pressure variation is assinged to the altimeter and by this I see this big changes on the altitude… can be possible or I´m totally wrong?

Dimitrios Kanellopoulos

@flypg On watch mode there is no mode

Dimitrios Kanellopoulos

@flypg for indoor activities there is automode

Dimitrios Kanellopoulos

@johann-fuehrer yeah I see the same from my sources indeed looks like the watch is about 6hpa wrong right ? There is a tool that can calibrate the abs pressure but unfortunately only support can do that.

johann.fuehrer

@Dimitrios-Kanellopoulos is there any support here in Vienna which can do this?

Dimitrios Kanellopoulos

@johann-fuehrer I am not sure I am very far away (in terms of internal comms) with support stations etc

@Dimitrios-Kanellopoulos Thanks, I think that I need re-read all the post again

mario_b

@johann-fuehrer ZAMG does not report QNH ambient pressure. They take the temperature into account. Compare your pressure with the Vienna airport QNH value: https://aviationweather.gov/adds/tafs/?station_ids=LOWW&std_trans=translated&submit_both=Get+TAFs+and+METARs
They are reporting every 30 minutes. (Time is shown is UTC so don‘t get confused)
You can only compare the ZAMG value when it is around 15 degrees Celsius in Vienna.
Greetings from Tirol

Dimitrios Kanellopoulos

@mario_b oh. Thats why the variation!

mario_b

@Dimitrios-Kanellopoulos thats why i allways ask, which ambient pressure is used to compare. because QNH is allways calculated with 15 degrees.
and since my a3p is back from service, its spot on with every QNH value around me.

freeheeler

@mario_b
15’000km service?!
what was wrong with it?

johann.fuehrer

@mario_b Hm, then I do not understand that:
LOWW at 8:50 local time: 1020 mBar at 22 degree Celsius, altitude 183m
ZAMG reading of Schwechat, 9:00 local time 1019.8 (998.6) hPa at 22.1 degrees Celsius, alt 183m
ZAMG reading in Vienna at 9:00 for all stations in between 1019.4 and 1019.9, of course depending on altitude and temerature, which varies about 2 degrees Celsius.
My reference from yesterday, Unterlaa at 9:00: 1019.6 mBar (996.6) at 21.8 degrees C, alt 200m
My reading on the watch: 1024 hPa at 22 degree, alt 209 m

So it’s off about 4 mBar. Or can you explain this?

johann.fuehrer

@johann-fuehrer … that would be an altitude difference of about 35 m. I used this calculator: https://www.mide.com/pages/air-pressure-at-altitude-calculator

mario_b

@TELE-HO more a 1000km service. but to be honest. it was nothing wrong. just a few other guys had the same value with ambient pressure, and mine did not match them. but altimeter worked flawlessly.
i have to say thank you again to @Dimitrios-Kanellopoulos and the awesome suunto customer service for help. they wanted me to send the watch in to check if everything is ok. they’ve exchanged the pressure sensor. now it is spot on. i was just tooo nitpicky. (also i know that it will show a different value over time).

freeheeler

@mario_b
my experience with Suunto customer service is one of the best I’ve ever experienced!
My wife had problems with her A3R from start (battery capacity calculation etc) and it was fixed within a week

Ok, I did not expect huge problems with your watch, good to know

I did not play around on the baro settings, I actually only use the alti mode and really never look at the baro itself.
But it was a very good hint from you regarding the fused alti and when it kicked in. Next time I will know, thank you!

mario_b

@johann-fuehrer just to be sure:

you know the exact elevation you are when reading your watch pressure? and the altimeter is set correctly?
you did the fridge test which @Dimitrios-Kanellopoulos mentioned above?
you are not inside a building?

mario_b

@TELE-HO yes suunto service is fantastic.
no it really didn’t.

on small hikes i do not record it, but wanna know the nearly correct elevation. and a guy from search and rescue (with an a3p) told me: if you look at the nearest weatherstations ambient pressure and compare that with your watch, you know about +/-10-15 meters if your elevation is correct, without the need of activating gps. and that works very well.

johann.fuehrer

@mario_b said in Doubt about Suunto 9 Baro altimeter/barometer calibration:

@johann-fuehrer just to be sure:

you know the exact elevation you are when reading your watch pressure? and the altimeter is set correctly?

Definitely!

you did the fridge test which @Dimitrios-Kanellopoulos mentioned above?

Yes, coming back to exact the same altitude. In my opinion it was very quick, some 5 minutes. But I’ll do it again if you like.

you are not inside a building?

No.
I did check this also inside the office (open windows), so ambient pressure inside and outside should be equal, no aircondition and the behaviour is the same like outside.