How do touch type heart rate monitors work?

[kpk250]

Hi,

I just spent an inordinate amount of time sifting through various articles on the web, but none answered my question adequately. Most were geared towards consumers of exercise heart rate monitors and offered very little technical information.

 

I know four types of touch heart rate monitors:

1. Oximeter - optical - uses two LEDs one IR and one near red and a correlating comparison light absorption function.

2. Chest strap - electrical - skin contacts pick up electrical signals.

3. Grip type - electrical - found on exercise equipment and usually consists of four metal pads (two on each hand grip) that the user squeezes while exercising.

4. Finger touch type - electrical - fingers touch two buttons on a watch.

 

My questions are:

1. How do the electrical versions work? What are they sensing exactly and what is the electrical measurement (resistance, capacitance, etc.)?

2. Is this measurement limited to certain areas of the body? Will it work inside the mouth? Nose?

3. What effects the measurement and how accurate is it? Sweat? Bodily fluids? Mucous?

4. Can this measurement be made with only one contact? A single metal plate.

 

Thank you,

Kris

 

 

 

 

Edited March 19, 2013 by kpk250