Doubt about Suunto 9 Baro altimeter/barometer calibration

A Former User

@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.

mario_b

@johann-fuehrer so maybee it should be recalibrated. i would ask the support.

johann.fuehrer

@johann-fuehrer said in Doubt about Suunto 9 Baro altimeter/barometer calibration:

@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 air condition and the behavior is the same like outside.

Finally, meetings are over: watch was 1 hour in the fridge @ 8 degrees Celsius:

10:00 before fridge, 1024 hPa, 30 C, @ 210 m
11:00 immediately after taking out the fridge, 1024 hPa, 8 C, @ 210m
11:15 another 15 mins later…, 1024 hPa, 25 C (still going up) @ 210m

LOWW & ZAMG still at 1020/1019.5

Dimitrios Kanellopoulos

@johann-fuehrer if not affected by temp your sensor is pretty well clean and no defect

mario_b

@johann-fuehrer are you at the “Umspannwerk Südost”? that’s the only point which is on 200m elevation. according to different maps, the rest of unterlaa is between 165 and 180m of elevation.

johann.fuehrer

@mario_b I had been, but now im at Hauptbahnhof/Belvedere which is (funny) also at 200m (Info from Geodatenviewer, wien.gv.at).But the pressure in different altitudes here in Vienna is not that big at the moment so that this would have an effect.

mario_b

@johann-fuehrer if the baro works, so altimeter is correct, meanwhile i would not mind, because i know over time it slightly drift anyway. but if you care, i would contact the support. the support is really great and helpfull.

Fatih Kale

Hi all,

Yesterday I ran on a track while raining so watch was covered by my jacket.

When I check altitude profile it’s veird. It shows that I went downhill but it’s not possible as I was at the same location turning around. Why could this strange values observed?

Here is altitude profile
link text

Here is the temperature graph
link text

freeheeler

@Fatih-Kale
I’ve seen a similar behavior with my Suunto Core some years ago.
When the sensor is covered or in contact with wet skin it seals off and or has a pumping effect.
I would expect that this wrong measurement is detected by fusedalti, but until today I still don’t understand how fusedalti works in detail and what it does over an entire activity or when for some reason the alti is completely off reality.