[Watch] SSU : altitude changes with temperature

[Mff73]

Hello,
I would like to present you one thing that drives me crazy these days with my SSU (with baro) watch.

I know that the altitude is calculated from relative atm pressure mesurements, given a reference altitude/atm pressure.
And I also know that there is a temperature compensation inside watch to correct physical relation between air temperature and read pressure, and then altitude. Everything works perfect with my old Ambit1.

But these days, with my SSU, I more go outdoor with friends or familiy, and I often need to wait for them, and for each pause I gain meters and meters of descent first, and when I walk/run again, ascent is coming.

I really think this is due to temperature : when in movement, air near sensor is also moving, and temperature is quite soften, but when stop moving, body temperature impact sensor, and altitude decrease --> D- is increasing.

Let’s watch this video where i try to simulate this : I start a move with my trail profil (alti settings)
My video
1- watch has not been worn since minutes to let it have stable temperature : altitude 545m
2- i only put two fingers behind watch to warm it --> -9mD- lost in 30s, and when I put my fingers away, altitude increase, and D+ increase.
3- and I can repeat this process, each time I loose meters and meters. Even more, when body is very hot like these days, and when I stop moving it can be 15mD- lost in a one or two minutes pause.

In movescount, temperature recorded for this test, in not in relation, you can see altitude profile for this two minute record, with no real change in altitude, but only fingers behind and away.

What do you think about that ?
Someone can test with his watch, maybe mine has faulty sensor ?

[Mff73]

A comparison of my today move with my SSU red, and my wife Ambit1.
Same path, just some pause for me :

[sartoric]

@Mff73 said in [Watch] SSU : altitude changes with temperature:

My video

For sure there is something wrong. In your case you have also negative Avg speed.
I’ve done “your test” with my baro and it works as expected, just got some few meter asc but I suppose it’s due to gps altimeter fix.

Have you already tried a reset / reflash ?

[Mff73]

@sartoric
Thanks for the test.
And yes, I have done 12s reset, and firmware flash as well.
Maybe it is time for my SSU to go back Finland for some guaranty expertise.
I will let some other experts here tell me their feeling before

[Dimitrios Kanellopoulos]

Looks like a problem I need to report!

The temperature of course affects altitude but it should not when paused.

[sartoric]

Maybe there is something wrong with GPS receiver (or the accelerometer ?).
Also the average speed changes significantly

[Dimitrios Kanellopoulos]

@sartoric good point

[Mff73]

@sartoric said in [Watch] SSU : altitude changes with temperature:

Maybe there is something wrong with GPS receiver (or the accelerometer ?).
Also the average speed changes significantly

Hi,
My video was made indoor, so GPS was certainly awful.
But this phenomenon is totally the same than when I am really outdoor for activity : pause in movement (but not a pause in recording activity).

Hi @Dimitrios-Kanellopoulos , thank you for reporting, and I can send you fit files for my last faulty move and my wife’s one to compare if needed.

[Mff73]

@Dimitrios-Kanellopoulos said in [Watch] SSU : altitude changes with temperature:

Looks like a problem I need to report!

Hi,
I can reproduce my issue 100% times.
I have just unworn my watch from my wrist, altitude was 520m, 1min after, 530m.
And when put watch on my wrist ragain, 30s only after and altitude id 520m again.
All that on watch mode.

Should I open à ticket ?

[Dimitrios Kanellopoulos]

@Mff73 Hey hi! !!!

Can you shake it? It should change then as well and that is a pressure sensor issue.

I just now did the test with running and my Alti changed 1m only and that was due to GPS alti.
Take a Look:

This is a 5m pause.

IMHO it looks like a faulty sensor or the sensor got dirty etc.

I had my dad watch with the same issue. These are the tests I did:

• I shaked it and changed alti.
• Make sure you shake it in a way that you “bang” the pressure sensor grill on your palm. That should shake the sensor vertically and change the altitude.
• Temperature as only it self should not matter.

But there is a solution as well.

Hot water at ~35 and:

• Leave it in a glass or have it running constantly on the pressure sensor grill under the tap.
• Flush again
• Very soft toothbrush if there is debrys.

If the above do not help then please ask support.

PS. If you are leaving in a humid area that affects even more a ‘dirty sensor’

[Mff73]

Thanks for tips.
Shake this evening and no effet, but I am waiting for after shower revival
Yes, another symptôme, after shower, or hand in water, altitude decrease by around 80/90m, and stay constant during more than 2 hours.

Will try thé warm water and see.

[Dimitrios Kanellopoulos]

@Mff73 the water gets in? Then its normal.

[Mff73]

@Dimitrios-Kanellopoulos
Yes, but 2 hours to get out
If I put my old ambit 1 in water and Shake it, I retreive good altitude in à couple seconds.
With my SSU, now, whatever I do, I have to wait.
For now, watch is in warm water. Let see.

[Dimitrios Kanellopoulos]

@Mff73 oh. Something is funky. Mine comes back at about 30m Max after poool swimming 1hour. Both s9 and ssu. From what you say looks kapot.

[Mff73]

Hi folks,

My ticket is on the way

Let’s wait and see, I will let you know

[valdis830]

Temperature affects, but I think not so much. Around 0.6 m for each degree ??

[Mff73]

@valdis830
I think the same, but, it is the only parameter that I think is modifiés when I just put my finger behind thé watch.
No news from support for now.

[Mff73]

Support answers me to restart watch and let it on table for a day (for électrostatic reason) and if nothing better, send it to Finland.

My SSU is on the way to Finland
Wait and see : repair/replacement or maybe they will find nothing

[Mff73]

No news from Finland, but since then, I re use my Ambit 1, and Altitude doesn’t change without any reason, and after shower, just shake the watch to make water out sensor, and altitude becomes correct (more than two hour with SSU).
I wait eagerly my spartan to come back to see how it works

[Dimitrios Kanellopoulos]

@Mff73 try blowing gently air in the spartan. It takes then 1minutes.