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Fenix 7X SS 14.36 - sudden massive changes in barometric pressure

Cuiv
over 1 year ago

I'm not sure when this started, but I'm seeing wild changes in my Fenix 7X SS barometric pressure.

Basically in the span of a few seconds, with the watch being on wrist or even static on a desk, the barometer reading will change enormously. For instance go from 1013 to 1024, then stay there for an hour, then suddenly go to 1003, then after a few minutes suddenly to 1013 again, etc. This is just an example, but if I look at my baro graph, I see basically a step function.

The altitude also changes massively, often going to negative altitudes.

This is in a stable environment, watch is static, baro ports are clear, no changes in weather outside (checking air pressure online shows it stable at around 1013), just those wild changes with the barometer.

What is going on? Is anyone else seeing this?

  • 0 over 1 year ago

    Often overlooked with these symptoms is that (ignoring altitude from GPS) the two actual sensors are air pressure and temperature (altitude is derived along with calibration).  I had a Fenix 5 with similar symptoms to you and the cause was actually the temperature sensor. You can add this to your glance options and check it out. 
    Additionally, although you will need to search (or someone else will be able to help) there is a diagnostic mode. Also an app PSX-8 RawData will pull these things out. 
    I remwber with the F5 the problem was initially only occasional then got worse and required a replacement. Naturally support wanted a master reset first. 
    I’m  being pessimistic here but may provide some useful information. 

  • 0 over 1 year ago in reply to razmichael

    Thanks so much! I looked at the raw data in PSX, and also in a connect IQ data field, both of which get the raw (but not yet filtered) temperature corrected barometric pressure.

    The raw value and the value displayed in the watch are completely different, with the raw value looking like it is accurate.

    I'll try to contact Garmin support, but for now I'm trying a master reset...

  • 0 over 1 year ago in reply to razmichael

    I'm getting really confused... I did another master reset, and this is what I see once it's completed:

    - Displayed Baro pressure: 1003

    - Raw Baro pressure: 1013 (correct!)

    - Altitude: -68 (I'm not in Death Valley)

    So I simply manually calibrate the altitude via DEM which gives the correct reading of altitude at 24m. And now I get:

    - Displayed Baro pressure: 1013

    - Raw baro pressure: 1024

    - Altitude: 24m

    So it seems that it's altering the Raw Baro pressure to fit the new calibrated altitude? And keeping a 10 hPa difference between baro pressure and raw baro pressure for no reason? I'm so confused because this seems to make no sense whatsoever...

  • 0 over 1 year ago in reply to Cuiv

    The whole absolute air pressure vs barometric pressure vs adjusted to sea level barometric pressure is confusing and I’m not sure where how the terms you are using are being used. Here is a very old but still good explanation on ABC watches https://www.watchuseek.com/threads/altitude-barometric-pressure-and-abc-watches-explained.266991/

    In general BP is displayed/adjusted to sea level.so not the absolute pressure at the sensor. A weather station knows it’s altitude and temperature while the watch only the absolute pressure and temperature hence the calibration requirement.
    Anyway, the main issue it to watch for jumps in either sensors.