HRM Chest Strap - Not Connecting

[Sakly]

Mine last roughly 2 years. I use the thing every day and about 2.5MM/year - obvs different usage may give a different life. Belt gets washed every 8 days. JM2PW

Probably useful to give the same info about the H10 I use.
Sensor working for 3 years now, only issues when battery is empty or goes near to end of its life. Now always connecting via Ant+, but BT worked properly as well.
Still using the first belt, which came with the sensor. Never machine washed, only a single time washed with hand. This is probably 1-2 years ago. I only dry the belt directly after usage with a towel.

Heavy sweat at the end of a session causes dropouts, I assume this is due to sweat saturated belt and some impaired electrical function.

[Carl Watts]

I thought I would post some technical stuff here for you to be able to test the strap on your chest HR monitor.

One of the eventual problems with the straps is the Carbon conductor pads age with time and use. You can test the pads with a Muiltimeter on Ohms and the resistance of the pad should be around 100 to 200 Ohms per centimetre when new.

You simply lightly jab the Carbon with the tips of your multimeter probes into the strap 10mm or 1cm apart.

An old strap 2 or 3 years old will possibly read as high as 1000 Ohms, at this point the strap becomes unusable as it goes intermittent and or fails to even turn on.

I do not recommend putting the strap in the washing machine, EVER.

The best idea is to pre-soak the whole strap in the tub of hot water before you put it on, then just hand wash in pure water and towel dry it when finished.

If you pre-soak it with water it will not soak with as much sweat.

The straps with a removable sensor are the best, the last generation Garmin is great because the straps are as cheap as chips on AliExpress and you just unclip the sensor and throw the strap in the bin after 2 or 3 years. The disadvantage with these is you need to be able to use a screwdriver and not strip the plastic threads out when changing the battery.

Another great tip is unplug the sensor from the strap after use or at least unplug one side, this makes the sensor shutdown much faster and makes the battery last a lot longer.

A tip for Garmin if you are reading this, get rid of the CR2032 battery and design it to take the CR2450, this is only slightly thicker and heavier but you will go at least 3 to 5 years between battery changes at its like 620mAh instead of 230mAh. Its a total pain when it dies right before your workout or part way into it, the CR2032 only seems to last 9 to 12 months doing long bike rides 4 or 5 times a week.

The early Polar HR straps were sealed, they had a larger Lithium coin cell soldered into them that would last up to 10 years.

Speaking of soldered in my fancy Orbis Data log 2 towel rail RTC timer just failed on the last power outage, the CR2477 finally died after 10 years, I pulled it and modified it by putting in a CR2450 battery holder and wiring it to the board. The capacity will be less but its only being drained during power outages so chances are it will still go the shelf life of 10 years becasue the battery is flat by then regardless of capacity.

The CR2450 is widely available even at the supermarket and its cost NZD$7 for a Duracell and the CR2032 Duracell costs NZD$4.50. I would rather pay another couple of bucks and not have to change the battery anywhere near as often.

[MPx]

I thought I would post some technical stuff here for you to be able to test the strap on your chest HR monitor.

Thanks Carl....didn't know any of that! I think I killed my original transmitter when I changed the battery and over tightened the screws wrecking the thread on one corner. Sweat etc got in and the battery,etc., tarnished very quickly.

[Tsnor]

One of the eventual problems with the straps is the Carbon conductor pads age with time and use. You can test the pads with a Muiltimeter on Ohms and the resistance of the pad should be around 100 to 200 Ohms per centimetre when new.

Nice. I have the original failed belt and a failed replacement and a currently working polar pro belt all for polar H10. Tape measure I used was imperial only, but 3/8 is about 1 cm. Measured on the non-fabric pad on the back. Cheap auto range etekcity multimeter. Mine seem to be getting lower resistance over time, not higher. I may not be poking hard enough to get a good reading -- none of these are near 100 ohms.

Ancient original belt: 60-75 MΩ at 3/8 inch.
failed replacement belt: 300-500 MΩ at 3/8 inch.
currently working belt: 300-500 MΩ at 3/8 inch.

The straps with a removable sensor are the best, the last generation Garmin is great because the straps are as cheap as chips on AliExpress and you just unclip the sensor and throw the strap in the bin after 2 or 3 years.

FYI, DCRAINMAKER does some great wearables content. His solution for Garmin HR monitor dropouts is to use POLAR belts with Garmin HR modules. Go figure, surprised this worked. I suspect a new garmin belt would have fixed the problem too. https://www.dcrainmaker.com/2010/08/sol ... pikes.html

A tip for Garmin if you are reading this, get rid of the CR2032 battery and design it to take the CR2450..

Polar H10 is a CR 2025 battery although people do accidently or intentionally stuff CR 2032 in them.

Decoding the CR 2032 battery number...

C = lithium
R = Round
20 = diameter of battery in mm
32 = height of battery in 1/10 of mm

So CR2450 is 4 mm larger diameter and 1.8 mm higher.

[gvcormac]

I haven't been able to reproduce Carl's resistance measuring technique, but this thread did prompt me to learn that Garmin and Polar belts are interchangeable (with each other but not with Coospo).

So I now have 2 Polars and 1 Garmin that I can mix and match for research purposes.

Coospo is working fine after 2 years of near-daily use. (indoor ergs)

Garmin is working fine after 1.5 years of several-times a week. (outdoor running) Occasionally the Garmin gives bogus readings for a few minuts near the start of a run. KY jelly seems to prevent this. Saliva not so much.

Some day I'll try the Polar with KY jelly and/or the Garmin strap.

I wonder why the Garmin strap has two extra square electrodes.

[Carl Watts]

Mmmmm cheap multimeter ? just tried it on an AliExpress strap, 96.5 Ohms. make sure you are on the carbon, if in doubt move out towards the extreme left or the right of the belt and of course we are looking at the part in contact with the chest. I have a 40 year old Beckman HD110 and a Fluke. Pretty close readings on both.

Re the battery wouldn't you rather have a 3 year battery life ? you wouldn't even notice the battery difference in size, its weighs like another 3 grams hardly a problem either. The CR2032 was probably chosen based on availability years ago, its no longer the best choice for a new design.

The Garmin and old Polar stuff work great with the aftermarket belts. I order two at a time in different colours which helps ID your strap. I have Three in total, two Garmin ANT+ only clip on ones and a Garmin RUN.

The KY jelly works better with other sorts of strap on's.

[gvcormac]

I have a drawer full of 2025s and 2032s, and it isn't that inconvenient to change the battery every could of hundred hours of use. I have certainly crammed 2032s into devices that expected 2025s (the Polar, perhaps?). 2032s are the ones you can g.et for practially nothing everywhere.

Based on your description, I think I found the carbon. The Garmin's is only on the extreme square pads. The Polar has insulation on the center, and the ends are exposed carbon. Same with the Coospo.

Resistance approx 1cm longitudunal distance.

Polar T31 (ancient): 340 ohms
Polar H9 I: 436 ohms
Polar H9 II: 465 ohms
Garmin Dual: 1208 ohms
Coospo: 450 ohms
Kyto Gymlink (Ali Express special): 52 ohms

I have a drawer full of T34 and T31, but you get the idea.

Garmin is the outlier. When it messes up (which is rare), it give preposterously high readings for a mile or so near the outset of my run, not zero. This is cured (I think) by saliva, and prevented (I think) by KY jelly. But it doesn't mess up nearly as often as the H9s, one of which is practically new. Note: I always wet the electrodes when I put the strap on.

For a lark, I measured the Garmin with KY, in case the high resistance was contact with the probes. No difference.

Edit: Just measured the Garmin again, and got 700 ohms on the nearer-the-centre electrode.

[gvcormac]

Just for giggles, I measured the resistance between the snap connectors on my Coospo with the transmitter disconnected, after 1 hour on the BikeErg: 34 ohms, plus or minus 3. [Edit: I wonder if this was 34K ohms and I didn't notice the K. Damned auto-ranging. See my later reply to this thread.]

I'll contemplate how best to do a controlled measurement of all the straps. The problem is to equalize the quantity of sweat.

Maybe I'll try soaked in clean water to start.

[gvcormac]

Also, FWIW, here's an example of the bogus reading I sometimes get from my Garmin. [Is there some way to embed images here? I haven't figured it out, so see link below. Edit: OK, got it, but it is annoying.]

Generally, I put the Garmin on, wet it, and sit around for a few minutes before heading out. The bogus reading generally happens after a minute or two, and persists for a few minutes. Maybe wetting with saliva helps. And since I started using KY jelly a dozen or so runs ago, it hasn't happened.

[MPx]

[Is there some way to embed images here? I haven't figured it out, so see link below.]

The way most of us post pics is to upload them to a [free] hosting site and copy the direct link address here between img tags (which are typed for you if you click the image button when editing). I use Postimage, many others use Imgur, whatever you're comfortable with. Something like this

[gvcormac]

I'll start a new thread once I get some more sensible/repeatable results.

So I measured the snap-to-snap resistance of my four snap-on belts with clean hard tap water:

Polar H9 (somewhat used): 3.2 Meg ohms.
Polar H9 (harldy used): 170 K ohms.
Garmin Dual (heavily used): 780 K ohms.
Coospo 808S (very heavily used): 90K ohms.

Now I wonder if my previous after-exercise Coospo value was 34K not 34 ohms, and I overlooked the auto-ranging.

P.S. KY jelly gave same readings for used H9 and Garmin. Still, I think it may offer a more stable connection while running. The reported false HR is suspiciously close to my running cadence.