Touch type heart rate monitors? How do they work?
Touch type heart rate monitors? How do they work?
(OP)
Google has failed me. 
Can some one tell me how the touch/contact style heart rate monitors work? Usally on gym equipment there are two metal contacts you place your hands on. There are also the watch type that you place two fingers one each on different contact points.
I'm assuming/guessing your creating some kind of loop and your capacitance changes up/down with every heart beat?
2nd question would be if I took the watch style and just pressed it into say my fore arm or my neck with both contactors touching the skin would it still work? or is there some reason it has to be through your fingers?
Thanks a bunch!!
Joe
Can some one tell me how the touch/contact style heart rate monitors work? Usally on gym equipment there are two metal contacts you place your hands on. There are also the watch type that you place two fingers one each on different contact points.
I'm assuming/guessing your creating some kind of loop and your capacitance changes up/down with every heart beat?
2nd question would be if I took the watch style and just pressed it into say my fore arm or my neck with both contactors touching the skin would it still work? or is there some reason it has to be through your fingers?
Thanks a bunch!!
Joe





RE: Touch type heart rate monitors? How do they work?
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Touch type heart rate monitors? How do they work?
You can see ALL about one method.
Good on ya,
Goober Dave
RE: Touch type heart rate monitors? How do they work?
Charlie
Charlie Gill
--www.calibrator.com--
RE: Touch type heart rate monitors? How do they work?
Roy
RE: Touch type heart rate monitors? How do they work?
I was a biomed type guy for a part of my career. The opticals are much more reliable than what they put on the gym equipment.
The metal plates you touch on a treadmill or stair-stepper or whatever are just electrical contacts, though. The device has to pick up the extremely-low electrical impulses that trigger heartbeats. It's looking for the peaks that you see on an EKG. It's tough to do with just a couple of sweaty hands on metal plates...
Good on ya,
Goober Dave
RE: Touch type heart rate monitors? How do they work?
The typical optical oximeter actually uses two LEDs, one is red and the other is near-infrared. The oxygen saturation is calculated from ratio of absorbances of the two LEDs' emissions.
TTFN
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RE: Touch type heart rate monitors? How do they work?
They are instead looking at the resistance. They're just ohmmeters. Your skin contact resistance is fairly high. On the order of 5k Ohms. But, like any area resistor as you increase the area of contact, or the pressure, the connection resistance is going to change. If your ohmmeter is completely biased to see changes in resistance, it can easily see the periodic changes in your grip, or touch, caused by the systolic pulses.
Grab the leads of an ohmmeter in your fingers and look at the reading. It wants to wander all over constantly. All you have to do is watch that wander, (much faster than your ohmmeter normally does), for periodic changes - they're caused by your heartbeat.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Touch type heart rate monitors? How do they work?
Good insight! I'm not quite interested enough to take my NordicTrak apart yet, but if I have too much idle time one weekend....
Good on ya,
Goober Dave
RE: Touch type heart rate monitors? How do they work?
TTFN
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RE: Touch type heart rate monitors? How do they work?
I think it's probably not measuring body fat content because those measurements are not valid if you are exercising and sweaty.
Glenn