Altimeter Fenix 5

Add my Garmin 5 to the list of crazy altimeters (it is an early build that I just purchased from Road Runner Sports (was probably on the shelf for 8 months). Otherwise it seems rock solid (GPS tracks are good, good battery life, fair Bluetooth and ANT+ connectivity - at least better than the Vivoactive 3 I had for about 2 weeks).

I did check the Ambient pressure and it looks like it is responding mostly normally. It is very cold and dry right now ....

Good day - I have emailed technical support, but thought I would weigh in on my new Garmin with problems. I have read this thread and found it to be useful regarding how the altimeter and barometer work together. I have had problems with elevation and believe my watch is not working. I added the ambient pressure to a new activity and when I check it shows 4765 mbar. I manually calibrated my altimeter and barometer to a close approximation of my location and using sea level pressure measurements from Environment Canada. However the number still make no sense. I do not know if the temperature is used at all for calculating the barometer value in the watch but I think that is my problem. It has fluctuated from -125 °C to 40 °C. I believe this is my problem because the barometer number has not changed since I manually calibrated but the apparent temperature has dropped by 10 ° and the altitude has dropped 100 meters (while sitting at my desk).
Should I ask for a new watch from Garmin or wait for the tech support line to offer any other suggestions? I like the other features of this watch but it has been disappointing to jump into the GPS world of sport watches with this disappointment.

Today my Garmin Fenix 5 Altimeter, Barometer and Temperature sensors were spot-on. Counted floors correctly too (first time in a while). Not sure what was different from yesterday where they were going crazy except it got above freezing outside today ....

The reason that your barometric pressure is correct is that it is an artificial value which is decided by the watch. When the ambient pressure measurement decided to go off, the watch decided to stick to the last known barometric pressure. But the relationship between ambient pressure, altitude and barometric pressure has to be respected, so the watch also decided to change the altitude to something wildly off.

The problem is your pressure sensor. It is defective. Or the air opening into the sensor is blocked. You should never, ever measure 862 millibar if you are only 100 meter above sea level.

I think you are wrong with respect to HW vs SW error. I've returned my Fenix 5 saphire and got a new one that has worked very well up until today. I uploaded a couple of new watch faces. Looking into the altimeter log it seems that it immedately after the upload of the watch faces the altimeter (and barometer) started to go nuts. There was no reason for the sensor to get broken as I was sitting still in my office. I think that somehow the SW reading the sensor has gotten corrupt due the new watch faces.

There was no reason for the sensor to get broken as I was sitting still in my office.

Give us some data!

From your watch:

• Barometric Pressure
  
• Ambient Pressure
  
• Altitude
  

From the world around you:

• Your real altitude.
  
• The pressure from a weather station near you, either as a raw ambient pressure or an MSL corrected pressure.
  

Then wait until the pressure at the weather station has changed 5-10 millibars and post the new readings from the watch and the weather station.

Please keep posting. This is really interesting. If it turns out that you can affect the ambient pressure reading by installing and uninstalling watch faces, it might explain why some users have had the same problems on several watches.

I can't remember if it was already posted in this thread, but some F5 users have found out that static electricity from their clothing could affect the pressure reading. So you should be careful with that while testing.

Maybe the relative humidity around the sensor plays a role in the erroneous readings. I am thinking that very low relative humidity might be causing a problem (would also correspond to the static electricity from clothing affecting things. Today my readings were again all over the place in auto mode - switching to altimeter mode keeps it more reasonable .... I was getting storm alerts inside our building (the air temp is 10 F outside with a very dry airmass in place right now after the coastal bomb storm.

Yes switching to Altimeter mode in my case seems to be fine. The Auto mode in my opinion seems buggy. My understanding reading a bunch of threads is that in Auto mode the watch tries to detect when the ambient pressure variations are due to changes in elevation or weather related.

As a side note thanks AllanOlsen67 for meteo terminology explanations.

I'm worried that Garmin does not seem to address this issue. There are reddit and forum threads reporting similar issue back to F3.

Yes switching to Altimeter mode in my case seems to be fine. The Auto mode in my opinion seems buggy.

Altimeter Mode is only fine as long as the surrounding pressure at unchanged altitude doesn't change. So in the long term (over more than very few hours), Altimeter Mode will be of no use unless you calibrate the altimeter all the time.

The Auto Mode can only be considered buggy if we see it making choices which would never make sense in that situation.

Just making the wrong guess based on a sound decision algorithm is not enough to consider the Auto Mode buggy. There will be plenty of those wrong guesses because the watch has insufficient information to always make the correct choice. In fact, I think that the biggest problem is users unable to understand this.