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HRM Dual dropouts

simondaw
over 1 year ago

I'm a long term Garmin user. I've had four Edge GPSs, and (I think) six HRMs - I managed to lose two (really reliable!) ones in the past two years. 

Almost exactly a year ago, I bought a new HRM Dual. I used this with both an Android tablet, running Zwift, and with an old Edge 1000. I also used one of the really old Garmin HRMs for some rides, and because the 1000 didn't record the sensor used I no longer know which I was using for which rides (except for Zwift - the old HRM didn't have Bluetooth of course). 

Anyway, although I didn't spot it straight away I think there was a problem straight away. I was getting short dropouts - just for maybe three or four seconds. These did not happen when the HRM was connected to the tablet - at least, I can't find any examples. I have very few rides recorded on the indoor trainer, but using a Garmin head unit, but I also can't see any dropouts on the (only) one I've looked at. In May, I replaced the 1000 with a 1040, and the problem continued completely unchanged. 

A few days ago, as the HRM was nearing the end of its waranty period, I contacted Garmin Support who were, I have to say, just superb. They replaced the HRM without quibble, and very quickly. However, I still have exactly the same problem! 

I wonder if it could be caused by a conflict with another sensor, but as far as I can tell there's no correlation between its use with various other sensors - a Varia tail light, and three different power meters (2 x Power2Max and a pair of Assiomas). Behaviour is the same whichever power meter is being used, and regardless of whether the Varia is in use. 

The problem occurs rarely, if ever, during high intensity efforts. This is a 22km time trial a few days ago, and is fine -

https://connect.garmin.com/modern/activity/11733022041

Whereas this - with dropouts, if not the worst - is a recovery ride a couple of hours later -

https://connect.garmin.com/modern/activity/11734314720 

I could probably live with that, but the problem has frequently become worse, with major drops for extended periods, like this (with a new battery, by the way) - 

https://connect.garmin.com/modern/activity/11623697997

Although the (a...) HR has recorded for much of the above ride, the final forty minutes is far lower than reality, and actually if you check respiration you'll see that it had basically failed for the last hour of the ride. 

So - I have tried:

  • A variety of clothing - so not static, I'm pretty sure
  • Batteries. Lots of them - different makes, different power ratings, original ones, replacement ones...no difference.
  • Position - high, low, left, right. Sometimes moving it makes a difference, but it doesn't sort the problem out. 
  • Pairing and unpairing. Lots of times, including mid-ride. No difference.
  • And obviously two head units. No difference.

Does anyone have any ideas?! 

  • 0 over 1 year ago

    Considering that those kinds of dropouts only happen occasionally and on just part of the activity (and with two HRM units), it could hint at poor skin contact (your posture somehow changes when you tire and bike outdoors?), although in my experience poor skin contact problems usually occur at the beginning of the activity because sweat helps keeping the contact.

  • 0 over 1 year ago in reply to Bitti

    Thanks for the reply. It's obviously one of the possibilities, but it's hard to see how. The fit is good, and the dropouts correlate with low intensity, not fresh / tired. They definitely don't correlate with "likely to be damp / dry" - not even slightly. I should also say that when warming up on a turbo for the time trial linked in my OP, but using the 1040 to record instead of the tablet I tend to use for indoor activities, I experienced dropouts. The common factor for dropouts seems therefore to be the Garmin head units (or possibly ANT+, as opposed to Bluetooth) rather than actually in/outdoor. 

    I should also have said (there are a lot of variables involved...) that:

    a).  I also use the HRMs with my iPhone, with the Elite HRV mobile app. It occurred to me today that just possibly the phone - which I also use with Connect paired with the Garmin head unit - might be trying to connect to the HRM via Bluetooth at the same time as it's connected to the 1040 via ANT+, and that maybe this might be causing issues. That would explain the perfect behaviour with the tablet - it connects to that via Bluetooth, and since Bluetooth maintains only one connection the phone wouldn't get a look in. I therefore unpaired the HRM from the phone and tried a ride tonight, with the new HRM. It's much better than the old HRM, but having only used the new one once I can't really tell if it's better or not, and I still had three very short dropouts - basically, what I had when the "old" HRM was new, I'd say. 

    and that

    b).I set up the 1040 by transferring my setup from the 1000, so it's possible that I've exported a gremlin.

    Given what I've observed this evening, I don't think it's "a", unfortunately. I think my next step is to do a factory reset on the 1040 and to do a clean setup. 

  • 0 over 1 year ago

    I have the same problem with hrm dual with forerunner 55. I have constant drop outs and it reads low readings while I am running, like 90bpm.

    I have took it to the shop and they replaced it with a new one and it still does the same. I cannot figure out what is the problem.

  • 0 over 1 year ago in reply to 4256659

    Thanks for the reply. 

    After my earlier posts, I both tried a hard reset and setup from scratch on the 1040, and also pairing the HRM with just the 1040, so that there was no chance of another device's connection causing the problem. Neither made the slightest difference - the dropouts were unaltered.

    So, in summary, two completely different HRM Dual units have shown similar behaviour. this behaviour is identical across two different Garmin head units (of different models). A previous Dual HRM worked perfectly, however (until I lost it...)

    i then found this video - https://www.youtube.com/watch?v=6VOblMXbJks . Apart from the video itself, the comments are informative - it appears to be a very common problem. Interestingly, I have the same (strong) correlation between zero cadence / power and dropouts.

    In my case, the dropouts are ALWAYS on "easy" rides, and never on high-intensity rides. Not only that, but, for example, when I did three sessions last Thursday - a warm up of 10 minutes, 23 minute time trial, then a 10-minute cool down, the dropouts occurred only on the warm up, even though the cool down was at much lower intensity. This both rules out the idea that it might be due to some change in position "when tired" that was mooted by someone earlier, and also suggests that the behaviour of the HRM and / or it's interaction with the head unit changes (for the better) when the HR increases. 

    The issue COULD be static related, but it's hard to see how - given the above example (which is repeatable) it seems unlikely that static would reduce. In any case, the problem doesn't seem to correlate with clothing I'm wearing. 

    The ony conclusion, really, is that it's an issue with the device in its current form, possibly general but at least very common. The solution, as suggested by others in the video and comments, appears to be an alternative brand of HRM, unfortunately, and that's the route I'll take once this unit becomes too unreliable for me to stomach.