Wrist OHR accuracy when not recording activity

Thanks, proves my point exactly! When starting an activity it seems the WHR sensor is ‘woken up’ and then stays accurate, even after you stop the activity recording mid activity. It stays accurate most of the time, till the next time you rest, then it seems ‘low power mode’ is active again. When not starting an activity the HR sensor never gets the accuracy right, at least not consistently. Surely a bug and one that is in need of fixing.

Hello jallamannen,

I also try to understand the wrist OHR of the Forerunner 945. Up to now I’m using the “Auxiliary Heart Rate” data field to compare the OHR to a chest strap. See also https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-945/174081/compare-ohr-and-chest-strap-hr-values-of-an-activity-in-garmin-connect

I can also not confirm the OHR is very good during activities for me.

OHR is very bad in activities like: cycling, fast changing HR (intervals, Stand-up / Sit down, …)

OHR is for me not so bad during steady state running / hiking.

When the OHR is has more than 20bpm difference to your real HR, the OHR will not catch up. Even when you try to help him with increase the intensity.

If I really want my firstbeat metrics to be correct, than I have to use a chest strap!

I have some questions to your analysis:

1. Have you paid the 29$ per year to use https://analyze.dcrainmaker.com (see image below)?

2. Which “activity type” you are using for tracking a day in the office? I have the impression that the reaction of the OHR depend on the activity type. During outdoor running and cycling it is really hard to bring the OHR to values below 100bpm. During hiking the OHR has no problems with HR values below 100bpm.

3. You are sure that the OHR is in low power mode when “broadcast HR”. I would assume that this is an activity too. → Not easy to get 24h wrist OHR values if you do not start an activity and at the end you have a fit file with the values.

Hi Ralf_23,

1. Yes, I bought the service as I use it to compare my power meters. I've also tried the Auxillary Heart Rate, but because of the axis issues in Garmin Connect I found it more useful to put the Edge 830 in my pocket and record there. Also tried talsela method of exporting to Excel, but still found the DCRainmaker Tool easier to use.

2. On FR945 I created a new activity based on Other, and just named it HR. On Edge 830 I created a copy of the Indoor profile and named it HR

3. I cannot be 100% sure, but seeing the OHR that much lower when broadcasting it, it confirms what I'm seeing in day to day use of the device.

Hi jallamannen ,

I’m completely surprised by your first plot “day at the office with some walks”.

I have not such good result for me. I made some tests with the “Auxiliary Heart Rate” data field and the cardio activity. The changes of my HR (when standing up to go for a coffee) are too fast for the OHR. As the Y-Axis are so different it makes no sense to plot the result here.

But I do not know how long I still will testing my wrist OHR. Therefore I’m not sure if it make sense to pay 29$ for the tool (https://analyze.dcrainmaker.com).

At the moment I only see 2 options for me:

Option 1: Stay with my Revison C watch and use chest strap for all of my activities, which have impact on my Firstbeat Statistics and believe that 24h HR tracking with Stress and Body Battery is “state of the art”.

Option 2: Change my watch and hope that Revision D, E, … OHR sensors are better. I can also not connect to WLAN with my actual watch. But I have no indication that Revision D, E, … has better OHR Sensors.

Hi Ralf_23,

If using the Auxillary Heart Rate field, you will in the DCRainmaker Tool get two separate graphs, with no options to overlay them. The tool is only useful if you can record on two devices so that you get two .fit files.

I was not aware there are different revisions of this watch. How to you check which revision you have?

Since the OHR to me seems perfectly capable of being accurate, I hope this is simply a software bug. Hopefully Garmin reads these forums.

I will also gather some more data, and send a support request to Garmin to see what they have to say.

Hi    jallamannen,

1. For the DCRainmaker Tool I can also use the Polar App to create a tcx file with chest strap. For biking I can also use my Bosch Nyon to create an independent tcx file.

2. The revision of the watch is printed on the box. At the low right end of the attached picture in the "red box".

I have the same behavior on my 945 - but with worse results at the beginning of my activities. While the real HR is rising "fast" the OWHR is dropping most of the time - often in showing half of the real value.

In case of my activities i dont care, because i use a chest strap and when recording an activity it is ok. But all the 24/7 metrics are wrong. Short activities like my commutes always have max OWHR of below 120 (without recording an activity) while my EDGE is recording avg of 140 - 150 with max of 180.

Also climbing stairs (4 floors at work fast) my OWHR usally stays under 90 bpm instead of 120+.

# Edit: Rev. D

I'm actually amazed by how far off the OWHR is during all-day tracking. As it is now my 945 is a pretty pathetic activity tracker and all the metrics (body battery, stress, HR, etc) are unreliable / useless. During activity OWHR is miles better, so the watch can (and should!) be more reliable as an activity tracker.

My watch is a rev. A by the way.

Me, on the other hand, have never had such a good WHR as with the 945. I‘ve had the VAHR, VA3, Fenix 3 HR and the 645 Music. None has been that good. Sure, still have some spikes or drops here and there, but all in all it’s quite good (Rev. D btw).

On the flip side, I got some mushy/sticky buttons that I‘ve only seen on the F3 HR before (and there only after some time and only on one button). So, it’s not perfect either.