Teardown: Taking the pulse of a fitness watch

-August 07, 2017

Back in March, I told you about my dubious-at-best purchase success with a "mystery box" of fitness wearables. My teardown victim then was a Skechers GOwalk activity band; this time I'll tell you about (and dissect) its "mystery box" companion, the Bowflex EZ Pro strapless heart rate monitor watch.

Bowflex is primarily known as a manufacturer of home exercise equipment. Like Skechers, which makes fitness (among other categories) shoes, Bowflex apparently thought it'd be a good idea to expand its brand into wearables. And like Skechers, Bowflex apparently failed at this particular endeavor; nowadays, the only result that comes up when you search the manufacturer's website on the term "EZ Pro" is (for unknown reasons) a protein shake bottle.

When I first saw the words "strapless heart rate monitor" I got excited, thinking I might have another optical pulse rate sensor-equipped device on my hands. Alas, there ended up being no photoplethysmography here; the "ECG" acronym on the packaging is a tipoff:

How the EZ Pro instead works is that you put the watch in pulse measurement mode, place your fingers on the metal contacts above and below the watch face, and wait a few seconds for the electrocardiography results to appear on the monochrome LCD. It's a somewhat clumsy approach, reminiscent of the metal contacts built into the handlebars and armrests of some exercise bikes and other fitness equipment, although in this particular case it's not really possible to monitor pulse rate on an ongoing basis during activity. But it seems from my brief experimentation to be pretty accurate:

But I'm getting ahead of myself. Inside the box is some paperwork, along with the watch itself, of course, encased in a bubble wrap bag:

Freeing it from its plastic captivity brings it into full view:

Here's an initial peek at its backside, along with a closeup of its front face:

Time to dive in; the first step is to remove the tiny Philips screws in each corner of the back plate:

Here's what you'll find inside; the location of the user-replaceable CR2032 battery is perhaps obvious:

Interestingly, the internal assembly then lifts right out, leaving the four "mode" buttons exposed, along with the routing contacts from the ECG plates:

Here's the backside of the internal assembly after being freed from the chassis:

And here's its front side; as you can see, the battery's still connected. Also visible are the ECG mating contacts on the PCB, along with the flexible "switches" activated by the four side mode buttons:

And here are four quadrant side views of the still-intact internal assembly:

Flip it back around so the backside is in view, remove the six even tinier Philips screws visible in the above photo, and the battery comes into clear view, along with one side of the PCB:

What about the other side of the PCB? Separate it from the LCD, and here's what you'll see:

As with the Skechers GOwalk, the identity of the main IC is unfortunately obscured by black glob-top epoxy. Note the rows of contacts both above and below it; hold that thought for a moment. You can also see the etched areas in each of the four corners of the PCB, which "complete the circuit" when one of the four mode buttons is pressed. To the left of the epoxy is a rubberized elastomeric connector; to the right you can see the PCB-side contact for its mate, which instead ended up still stuck to the LCD assembly after I separated the two pieces:

And above and below the LCD you'll see the additional elastomeric connectors, which correspond to the earlier mentioned rows of PCB contacts.

Thus concludes this two-part teardown series on low-cost fitness wearables. I hope you've enjoyed it; as always, I welcome your thoughts!

Brian Dipert is Editor-in-Chief of the Embedded Vision Alliance and a Senior Analyst at BDTI.

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