Continuous HR registration from external sensor possible?

No, an external HRM only works in activities or, for short periods, with apps like the Stress Test.

Based on the comment by timgrose does anyone know why the watch is continually trying to connect to HR straps ie that it has previously connected with?
It does this when an activity is NOT selected.
You can confirm this by looking at settings.
Also if you undertake a Run/Walk activity using a Tri Strap and then save it, the data saved is based initially on OHR data that is until you download the HR data from the strap.

Well sounds like you have gone into the sensors & accessories screen and unsurprisingly there it is saying it is trying to connect to your sensors as presumably you put them there as you might want to use them. Whether it looks for them outside of being within an activity profile and not being in that screen is less likely. It certainly won't be doing so in low power mode (clock screen).

AFAIK the HRM-Run and HRM-Tri does continuously record your HR if you are wearing it even if you have not connected it to your watch. This then allows the download HR feature to have some relevance if the HRM was not paired or, as in swimming, it does not really work in real time.

Of those two only the HRM-Tri has this capability. The only other strap that can do this is the HRM-Swim.

Yes, good point! Well corrected.

Well if I am reading the above correctly when the watch is NOT in an activity (except for Stress Mode) it is "less likely" to look for HR straps in low power mode (clock mode).
Also if you are in settings looking at the sensors then it is only trying to connect while you have this option active.
Kind of like trusting that the fridge light is only on when the door is open.

I bought both the Tri and Swim straps due to the inaccuracy of the OHR data (when running and no HR data when swimming).
It may not have been clear in my post above but I consider it an anomaly if you are performing an activity (say run) and have coupled with the Tri strap before starting the activity, when you end that activity and save the results the OHR data is saved with the results, that is until you Download HR data from the Tri strap.
When the activity is saved the Training Effect readings are calculated based on OHR data and after the HR strap data is downloaded the TE data is recalculated.
TE data (for me) is always different after the download of HR strap data.

I don't know whether the HR Widget is classified as being in low power mode or not.
But there is another anomaly.
After a run or swim activity I put the Tri/Swim strap in my bag and have a shower.
In the dressing room I have noticed on several occasions that the HR widget will show HR readings of 70/80 then climb up to 240/250 then show "measuring" and repeat this pattern.
I was perplexed for a few weeks by this behaviour until I found that the watch was connecting to one of the HR straps in my bag.
It was receiving garbage data from a strap (an assumption) and displaying it.
I walked about 10m from my bag and looked at the watch sensor settings to see that the watch was still connected to one of the straps

In summary:
- The watch should not keep trying to connect to straps that it has previously connect with (unless there is an activity selected that is related to the use of HR strap data);
- If the HR widget is connected to a strap that is not being worn then it should not display garbage data;

I consider it an anomaly if you are performing an activity (say run) and have coupled with the Tri strap before starting the activity, when you end that activity and save the results the OHR data is saved with the results, that is until you Download HR data from the Tri strap.

This is not how it is supposed to behave. The scenario you described happens only when during the activity the strap is PAIRED BUT NOT CONNECTED to the watch - for example because it is under water or too far away. If the HRM-Tri is constantly connected to the watch during the activity, then the optical HR is actually off and does not register any data, and all data comes from the HRM-Tri strap. No downloading of data is necessary in this case.

I don't know whether the HR Widget is classified as being in low power mode or not.

No. Low power mode is in the watch face only. All other modes are not low power and any external ANT+ sensor might connect to the watch.

- The watch should not keep trying to connect to straps that it has previously connect with (unless there is an activity selected that is related to the use of HR strap data);

Many people - including me - would disagree with you on this.

- If the HR widget is connected to a strap that is not being worn then it should not display garbage data;

But how would the watch know if the strap is worn or not? If the strap sends HR data then the watch assumes it is being worn. And the strap itself is quite simply sending data whenever it sees electrical impulses on the electrodes - which might happen if the strap is in a wet bag.

I really don't think there is anything to worry about if it appears your device is constantly looking for your sensors. There is no obvious indication this adversely effects battery life to any significant extent. If you have sensors you don't want to connect to apart from in your control then keep the sensor pairing but set the status to Off. Then the watch will ignore it and nor it will it offer you to pair to it again if say you did Add New.

Thankyou tmk2 and timgrose for your feedback.

tmk2 you said:

This is not how it is supposed to behave. The scenario you described happens only when during the activity the strap is PAIRED BUT NOT CONNECTED to the watch

Try it. Start a Run activity and make sure you CONNECT with the Tri Strap (the watch will tell you if it has connected).
BTW the strap is on your chest and the watch is on your wrist; the strap is not underwater nor too far away.
Stop and Save the activity. The data saved is OHR based data. Check the TE results.
Next save the HR data from the strap.
See if the TE data and other activity details are still the same.

tmk2 you said:

Many people - including me - would disagree with you on this.

Why do you say this?
Isn't it a sign of bad system design to have functions active unnecessarily?
I don't really know what impact this has on battery life.

But how would the watch know if the strap is worn or not? If the strap sends HR data then the watch assumes it is being worn. And the strap itself is quite simply sending data whenever it sees electrical impulses on the electrodes - which might happen if the strap is in a wet bag.

I consider there is a flaw with the system as a whole.
Maybe the watch should filter/reject garbage data; maybe the strap should measure the resistance between electrodes and realise it is not connected to a human.
Maybe I am expecting too much.
Regards,
Nick

Try it.

I don't have to try it. I use the HRM-Tri regularly and never experience the issue you describe.

The data saved is OHR based data.

It is not. When I'm in an activity and my HRM-Tri is connected then the OHR is off which is easy to verify by looking at the green LEDs.

Isn't it a sign of bad system design to have functions active unnecessarily?

When I wear a chest strap I expect the HR data to come from the chest strap, even if not doing a sports activity, be it an IQ app, the HR widget or practically anything else. The only exception would be the watch face low power mode, but even then it would be nice to have HR data come from the chest strap, lack of which is understandable due to battery concerns.

I don't really know what impact this has on battery life.

None, I bet. ANT+ transmission is very power efficient. Just by leaving the watch face low power mode the watch starts consuming significanlty more energy than by connecting to an ANT+ sensor by itself.

Maybe the watch should filter/reject garbage data;

Deciding whether data is garbage or not is a complex issue. Any method of doing it would give wrong results in certain conditions.

maybe the strap should measure the resistance between electrodes and realise it is not connected to a human.

That's exactly what the strap does, as it goes to sleep when not worn for some time. But there are circumstances when measuring electricity on the electrodes is simply not enough to determine if the strap is worn or not.