Spark HR has become inaccurate

thomassteph
thomassteph Registered Users Posts: 18
Outstanding Explorer
edited January 24 in TomTom Sports
Is anyone seeing the accuracy of your HR data get worse? Lately my Spark Cardio HR + music is reporting very high heart rates, especially when running. Like it should probably be in the 140's and 150's and it's in the 160's and 170's. My watch is about a year old and this has been happening of late. It is even reporting 150s when I am casually walking my dog. Yes, I have done a few factory resets. Anyone?

Comments

  • tfarabaugh
    tfarabaugh Posts: 16,936
    Superuser
    Make sure the back of the watch is totally clean, that a film of sweat and grime did not build up as that will impact it. It also may be the time of year in that you are likely wearing short sleeves now, so more light can get in around the sensor (the enemy of OHR). You may need to tighten it up a notch to ensure there is a good connection. Other than that I would say do a factory reset, which you already did. If it continues, I would suggest calling Customer Support to see what they can do. They are able to more deeply investigate and diagnose problems than we can here on the user forum. To get the number for Customer Support, go to tomtom.com/support, choose Contact at the bottom, select the service required and the product name and click Contact Customer Care and then Phone Us. It will give you the phone number for the country your account is registered under (this can be changed by clicking the flag icon in the bottom right corner of the screen).

    In general, spikes in HR are usually from poor blood flow producing weak pulse strength, so the watch reads cadence instead. This is particularly apparent early in a workout or during a non-intense workout when you are not warmed up. You have to think of the optical heart rate as an algorithm that is attempting to track a signal in a set frequency range (30-230 or whatever it uses). If the pulse signal is weak it latches onto the next strongest rhythmic signal, which is your cadence in running and the vibrations of the bike in cycling. For most people who experience this while running it spikes to around 180-200 bpm which is also the average cadence people run at. Additionally, each person has a different HR signal ‘strength’, depending on a range of factors, so some are prone to get it more than others. But usually their signal strength is lower for the first 5-10 minutes until they warm up properly. So in that time, it is prone to latching onto cadence, which is a common fault with all optical HRs, unfortunately. If you notice it while it happening you can try moving the watch a bit or briefly pausing your run so it loses the cadence reading and latches back onto HR, which I find usually corrects it. I generally pause the watch, stand still for 20-30 seconds and will see it immediately start to drop. Once it gets into a more reasonable range and the pulse reading stops dithering (dithering is when it is not getting a good signal and it is a lighter grey in color) I start up again and it stays true for the rest of the run. You can also try switching wrists and the position on the wrist. I find I got better readings on my right wrist over my left and some people find they get better readings if the watch is on the inside of the wrist rather than the outside. It also helps if you warm up a bit to get your blood moving and your HR up so it is producing a strong signal. Play around with it and see if any of this helps you. The challenge for the manufacturers of optical HRs (and this is a common issue with all brands, my Scosche also does it) is to figure out how to factor out the other "noise" that is overriding the pulse signal without also factoring out other important data.

    I hope this helped answer your question. If so, please mark it as a solution so others can look for it if they have the same question.
  • thomassteph
    thomassteph Registered Users Posts: 18
    Outstanding Explorer
    Thanks, I will try some of those things. I already knew it works better on right, though I like it on left. I have tried moving it around and tightening it, to no avail. It has always been somewhat inaccurate, especially at first on a run. But there has just been a noticeable change lately to HR in 170s and 180s and it makes me wonder if something is wrong with it. Of course maybe these optical HR devices just will never be accurate, like a HR band with a Garmin is, and I should just give up on that.

  • elbo
    elbo Registered Users Posts: 49
    Apprentice Traveler
    You can also try to move the watch as far as possible away from your wrist. Your wrist is about the worst possible place for a OHR to work, and moving it up on your arm might improve things a bit.

    When I bought my TomTom runner 2 a couple of months ago I had hoped the magic word would be convenience: one device instead of a watch, cheststrap and mp3 player.

    Now I know the magic wordt is unreliable:
    1. ORM is unreliable: I have the same peaks as you have and even higher 200+ is quite common (my running cadence is around 160 - 175, so that cannot be the mistake the watch makes)
    2. Current pace is calculated wrong. Also changes in pace takes ages to detect. The watch is unreliable when running intervals.
    3. The music player is good enough, but the bluetooth connection is unreliable. Lots of hickups.
    4. TomTom is unreliable. They promise new functionality for ages, but don't deliver.
    5. Sleeptracking is unreliable. When you sit still (watching a movie) the watch counts it as sleeptime.
    6. The straps break easily, so they are also unreliable.

    My runner 2 is not good enough for excercises and not good enough as daily activitytracker. At least I 'only' paid 159 euro for it. And for lunchruns it's kind of a little bit good enough, just to get my lap in the park on Strava.

    edit: And I do like the daily rest heartrate. That really helps me to get insight wether I train enough or to much. (Ironically, OHR works quite well when you're not moving. How convenient for something on a sportwatch ;)
  • thomassteph
    thomassteph Registered Users Posts: 18
    Outstanding Explorer
    elbo, agreed, with all of those things. The magic word is indeed unreliable. I liked the music player and not having to run with a phone as well as the multi-function of having a swim watch too. But it doesn't do anything reliably or excellently. And TomTom provides no new functionality.
  • Crash486
    Crash486 Registered Users Posts: 13
    Outstanding Explorer
    The TomTom is out by , on average, 20bpm. This appears to me to only happened recently. I borrowed my sons garmin HR strap and hooked it up to my phone which confirmed the inaccuracy. Isn't there some way to calibrate the HR reading?
  • tfarabaugh
    tfarabaugh Posts: 16,936
    Superuser
    Crash486 wrote:
    The TomTom is out by , on average, 20bpm. This appears to me to only happened recently. I borrowed my sons garmin HR strap and hooked it up to my phone which confirmed the inaccuracy. Isn't there some way to calibrate the HR reading?

    You can't calibrate it, but a factory reset might help. To do a factory reset, make sure the Connect software is running and dock the watch to your computer. The Connect window will open; press the gear at the top right and select Factory reset from the next screen. Follow the steps provided, giving the watch the same name and using the same email address. When prompted to register or sign in to MySports, select sign in and use your existing account credentials. It is fairly straightforward and should take less than 5 minutes.
  • Crash486
    Crash486 Registered Users Posts: 13
    Outstanding Explorer
    Thanks for the info. I did a factory reset but it had no real effect on accuracy. I purchased an external BT enabled strap which I now wear for accuracy. Shame, as liked the ease of use . I find straps slightly annoying and an added complication.