Mark-T
Guest
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 Posted:
Tue Nov 08, 2005 9:34 am Post subject:
How does this sensor work? |
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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
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Charles Schuler
Guest
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| Posted:
Thu Nov 10, 2005 1:35 am Post subject:
Re: How does this sensor work? |
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"Mark-T" <mark-t2@lycos.com> wrote in message
news:1131420875.636310.302470@z14g2000cwz.googlegroups.com...
| Quote: | 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?
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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. |
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Mark-T
Guest
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| Posted:
Tue Nov 29, 2005 1:36 am Post subject:
Re: How does this sensor work? |
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Charles Schuler wrote:
| Quote: | 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?
Same way as an EKG. The electrical activity that fires the heart muscles
appears on the skin as a weak signal and can be amplified, filtered
and counted.
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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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