Barometer not changing but Altitude is - FENIX 5

Former Member over 8 years ago

Hi everyone,

Beginning to loose the plot in trying to understand the relationship between Baro, Temp and Altimeter on the Fenix 5.

Thought i'd looked enough into my teething problems to understand when to set the watch in Altimeter or Baro mode stuff like that. Alas im flumexed.

My Quesiton:
Whilst walking around London I'm seeing the Altimeter swing around quite a lot but the Baro isn't changing at all. I tried to understand the theory of Air pressure Altitude but it may be beyond my intellect.

I read on another post that some had had problems with Baro / Altimeter readings after swimming with a new watch.

Over the past few days i've seen my Fenix 5 read this for Alt & Baro,

57m 1023
36m 1022.9
13m 1022.9
-2m 1022.9

Does this look normal? After owning an early Fenix 3 and returning it after the precarious Altitude reading problems I don't want to carry on with the watch if there is something wrong.

Any help in me understanding this would be great.

Thanks
Glen

0 jim_m_58 over 8 years ago

When you view the barometer, you are likely viewing it as the pressure adjusted for sea level (that's what they report in weather reports, etc)

That sea level pressure is used in conjunction with the actual observed pressure at your altitude to determine the altitude.

Sounds like it's working fine to me. You shouldn't see the pressure change unless there's something happening weather wise, even if you change altitude.

0 rickj2903 over 8 years ago

I think the OP is saying that his altitude isn't physically changing but the watch is saying it has.

0 jim_m_58 over 8 years ago

I think the OP is saying that his altitude isn't physically changing but the watch is saying it has.

It sounded to me like the altitude itself was changing as expected, and he was concerned that the pressure wasn't:

Whilst walking around London I'm seeing the Altimeter swing around quite a lot but the Baro isn't changing at all.

I guess it depends on "swinging around quite a lot" means. I can walk around and see the altitude vary in a range of 100' (which is correct, with a hill or two), while the pressure I see stays the same.

0 Former Member over 8 years ago

Thank you so much all, appreciate the quick replies.

Its a vague memory..is it possible to change the Baro so it show Amibient pressure and not MSL pressure, I cant find the setting on the watch or in the PDF instructions. Maybe that would help understand the pressure readings.

I'll do some Alt/Baro records taken at the same known altitude. The 'walking around' was at similar altitudes (apologies for the ambiguous turn of phrase)

I guess the nub of my understanding centers around me understanding that if the watch is displaying MSL pressure and the watch is in Altitude Mode that the watch has no way to know if its an altitude change or a weather change.

0 Former Member over 8 years ago

Thanks so much everyone, appreciate the speedy replies :)

Just typed my thoughts but they vanished after trying to attach an image...I'll try again...

I dont think i've ever noticed the Baro stay on exactly the same setting for so long. The weather us unusually fine here in London though so perhaps its ok. The image shows the historical Bar readings as a constant 1023 yet the current reading as 1022.9 which I guess is the watch just rounding up.

The readings I popped in my first post were taken at roughly the same altitude, I'll record more readings from the same known altitude to confirm though.

Is there a way to have the Fenix 5 show ambient not MS pressure? In activities I can see a data field that offers the option to show Ambient & Baro pressure

(at the same time the image was taken these are the readings)
Ambient 1018
Baro 1023

Is Ambient the pressure where I am and Baro the MSL pressure?

My thinking is that the watch has no way to know (in Altitude mode) that pressure changes are from altitude change not weather change so if the Baro is constantly showing the same pressure (Ambient or Baro) then the Altitude should stay the same. I think im missing something here though. Perhaps this is the nub of my lack of understanding or watch error.

Thanks again everyone
Glen

0 Former Member over 8 years ago

Hi everyone... me again.

Gotta say Im no closer to understanding the 'sticking' Baro readings.

Been keeping a track of the Baro and Altitude and the only time the Baro has changed was when I calibrated the Altimeter (using GPS) The weather in Dorset and London has been full on storms and then blue Sunshine this last week so am sure the Baro should have changed on its own. When I calibrated the Altimteter the Baro suddenly changed from 1022.9 to 1012.3 (with a nearly a 100m Alt change). Since the calibration the Baro hasn't changed again despite contiuned dramatic weather changes.

Thinking its probably time to contact Garmin with a suspected fault unless my senior mind is missing something

39m - 1022.9 London home
87m - 1022.9 London home
99m - 1022.9 London home
122m - 1022.9 Dorset home

Reset using GPS
28m - 1012.3 Dorset home ( baro suddenly changed after calibrating altimeter with GPS)

-22 - 1012.3 Dorset coast.
-19 - 1012.3 Dorset home
23 - 1012.3 Dorset home

Thanks for reading (if you did :) )

Glen

0 JarekX over 8 years ago

Hi Glen,

Please let me know how it went with Garmin.
I seem to have the same issue. The barometer is flat while the elevation is changing.
Even on a flight where I felt the pressure change in my ears the barometer was flat while the elevation reading was changing a lot.

Thanks
Jarek

Edit:
-----------

Here is how it works according to Garmin Support:

quote:
------
These devices calculate altitude by comparing the difference in sea level and ambient pressures.
Taking advantage of the fact that weather pressure changes occur at a slower rate than a person going up or down a hill, the unit will automatically transition between two modes; Altimeter or Barometer. As an example, if a watch is on your wrist and on the same floor of a building, the watch will remain in Barometer mode, pressure will change slowly and will be reflected in a moving barometer value, but the watch will keep the elevation value locked. If you then go up or down a set of stairs, the pressure will change enough to cause the watch to switch to Altimeter mode. Accordingly, the watch will lock the barometer value and you will see changes in elevation values.
------

I tested it in a depressurized coffe jar. When the Fenix's barometer is set to Auto elevation reading changes but barometer not. When it is set to Barometer the barometer reading changes but elevation not.

I guess for proper storm detection it is better to set it to Barometer mode.

0 JarekX over 8 years ago

In my case all is clear now. Here is how it works according to garmin support:

These devices calculate altitude by comparing the difference in sea level and ambient pressures.
Taking advantage of the fact that weather pressure changes occur at a slower rate than a person going up or down a hill, the unit will automatically transition between two modes; Altimeter or Barometer. As an example, if a watch is on your wrist and on the same floor of a building, the watch will remain in Barometer mode, pressure will change slowly and will be reflected in a moving barometer value, but the watch will keep the elevation value locked. If you then go up or down a set of stairs, the pressure will change enough to cause the watch to switch to Altimeter mode. Accordingly, the watch will lock the barometer value and you will see changes in elevation values.

I tested it in a coffe jar that can be depressurized by switching the barometer watch mode from Auto to Barometer.
That worked as expected - elevation did not change but barometer reading did change from 1014 to 908. After the switching the mode to Auto elevation changes but barometer not.

I guess when you want the storm detection to work properly you need to set the watch to Barometer mode.

0 Former Member over 8 years ago

Hi JarekX

Not sure our situation is the same. I did look into the intricacies of the different watch modes a while ago. My understanding is that the settings define the behaviour of the Altimeter and that the Baro pressure should change regardless though I could be wrong. The Baro on my F5 used to change all the time until the 'something' happened :)

Had a strange 1hr 15min chat with someone at Garmin and they have kindly offered to send me a replacement.

Glad you got to work out your watch Baro.

Glen