At my gym, there's a cardio machine, like a treadmill, also with handles to push and pull. Something like cross country skiing. The handles have stainless steel plates, you place your palms over them, it reads your pulse.
How does it work?
Mark
Same way as an EKG. The electrical activity that fires the heart muscles appears have on the skin as a weak signal and can be amplified, filtered and counted.
hmmm, I'm skeptical -
EKG sensors use damp pads as interface, this device has a metal plate.
The electrical activity which you allude to is muscle action, and the EKG picks it up locally. But this sensor is at the palms, far from the heart.
The EKG actually has two pickups, which of course is necessary to sense a potential difference resulting from muscle activity. This sensor also has two pickups, but I doubt it's looking for a differential signal - the hands should be at the same potential, except for noise - so it must use some other method.
My guess is it's acoustic... mainly because I can't think of anything else...
Also, it detects when one hand breaks contact, which indicates it's looking for a common mode signal, above some threshold, that should rise above the background noise.
Mark
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