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Fenix 7X Pro HR sensor crazy readings

Cane
7 months ago

Hi all,

I was out for a run today, and from the start my heart rate reading was quite inconsistent with my usual effort/feeling and speed.

Since I was wearing the HRM dual strap I thought it could be it, it happened before with some t-shirt and a down jacket to have elevated readings for some reasons (electrostatic?), so I stopped and disable it, to use the OHR from the watch only.

With my surprise the OHR reading jumped to 175bpm... I was barely walking and for sure my heart wasn't running over 100bpm, so then I did the opposite: removed the watch from the wrist, and enable only the HR strap, and the reading went back immediately to 80bpm, which was consistent with my pulse and feeling.

Never happened before (1 year owning the watch), and I always found the OHR very good compared to the strap, not sure if it's the new firmware or just an isolated case, too early to say.

Anybody with a similar problem with the latest 19.34 firmware, or before?

  • 0 7 months ago
    Cane said:
    Anybody with a similar problem with the latest 19.34 firmware, or before?

    A very quick search of the forum will answer that. 

  • 0 7 months ago in reply to Dr Phil

    Not quite the same problem, the same watch, the same hr strap combo or firmware. But thanks for the effort.

  • 0 7 months ago in reply to Cane

    So, you've read every single one of the threads but insist you have a completely new problem with OHR?

    Issues with OHR from the latest update all the way back to the very beginning have existed for some people all the time. I strongly doubt you have a new problem. But who knows. if you believe you have discovered a new issue with OHR then you'd be best placed to contact Garmin Support, in fact do that anyway.

  • 0 7 months ago in reply to Dr Phil

    It is not just a problem with OHR. It is a problem with the watch replacing a good data from external HR sensor with a bad data from OHR.

  • 0 7 months ago

    Went for a easy run today for the first time since the watch updated. Fenix 7 watch only, no strap. It said my heart rate was 148 at the very start which is bonkers. It then climbed steadily to 176. I was barely out of breath so I just ignored it. About 5 minutes into the run it dropped instantly (a matter of seconds) from 176 to 132 (which is what it should be) and stayed around that for the remainder of the run. Definitely something not right.

  • 0 7 months ago in reply to Tris
    Tris said:
    Definitely something not right.

    Everyone knows that except Garmin and couple users on this forum.

    silentvoyager said:
    It is a problem with the watch replacing a good data from external HR sensor with a bad data from OHR.

    True. Dynamic sourcing feature Garmin introduces this year proved to be source of issues it was supposed to resolve - bad HR readings. 

  • 0 7 months ago in reply to Vizi
    Vizi said:
    True. Dynamic sourcing feature Garmin introduces this year proved to be source of issues it was supposed to resolve - bad HR readings. 

    On paper it's not a bad idea, but the data should be filtered by something more sophisticated than just replacement with another source. I'm pretty sure they have a huge dataset to train a working algorithm or ai model to do that.

    I'm going to disable the dynamic sourcing for the moment, maybe I'll do some test with the strap only, and later with the OHR only, no sure, I don't want to waste my training because of this.

    Unless there's some bug related to the dynamic sourcing, still doesn't explain why the OHR is getting reading so wrong all of the sudden. I was thinking about temperature, but doesn't look like something that should affect OHR readings.

  • 0 5 months ago in reply to Cane

    Having exactly the same issues @Cane. This with Fenix 7x Pro and HRM-Dual. Zwift Forum suggests reversing polarity in the HRM unit, by turning the battery over and holding for 10 seconds. I find the wrist HR more accurate than the HRM-Dual at the moment, and nothing else has changed other than replacing my Fenix 7x with Fenix 7x Pro (courtesy of Garmin) as my 7x altimeter went wrong from swimming. You'd have thought such a watch could cope with a bit of pool swimming........ Finding inaccurate heart rate, which haven't had a problem with before, really frustrating. Readings of 170+ from HRM-Dual, when only 120 ish on wrist HR. Weird!

  • 0 5 months ago in reply to Nick C

    I suspect that there's something going on with electrostatic charge (and low temps?). Actually I'm pretty sure, even if I'm not able to repro the problem 100% of the times.

    Note that I started to wear the watch over the jacket because I trust more the HRM strap, and because It's quite cold it's just inconvenient to hide the watch under the t-shirt and the jacket and gloves, so no OHR in the mix this time.

    Here's why there something wrong:

    it happened to me another 4-5 times, wearing the HRM dual in a particularly cold day: the bpm where again super off, and it's always in the first 10-15 mins of warm up, just couple of minutes after the temp switch from the interior to the exterior (I run outside, just the time to exit home and start the run activity).

    So, while running, and while it's happening, I tried to pull off my t-shirt from making contact with the HRM shell, and lo and behold, the bpm went immediately down to the right spot.

    Then I stopped pulling  the t-shirt, and boom, the bmp were again through the roof. Again I pull my t-shirt, and the bpm goes down. And again and again like this for 10-15 mins. At some point it just stabilizes to the right spot in zone 2, where it should be (static discharged? I higher temp reached?).

    When this happens it's always the same, I tried every time this trick of pulling the shirt from making contact with the HRM shell, and it always behave like this.

    So, it looks related to static of some sort (this I'm pretty sure), and it seems related to the particularly low temp (this I'm not sure).