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Heart rate monitor pickups the heart beat and transmit? How is done?

I would like to know in details how a Polar or Mia Heart Rate Monitor (HRM) pickup my heart beat and how it transmit the signal.

1) I want to know why does the HRM need moisture?

2) Why the paralleled grooves are important on the transmitter side of the HRM? There are two, one on each side of the transmitter?

3) What is the wave length of the HRM?

4) Is the length of the plastic "wings" are important for the transmitter or the pickup of the heart beat?

Does the antenna use a Yagi or coplanar antenna for the transmitter and for the reception?

5) Has every knows the heart is submerged in a saline fluid where only Ultra Short wave length can reach the heart due this saline solution. How does the HRM picks up the heart beat? Is it by induction? Is it by conduction? Is it by using OPamps? etc

6) How does the electronic circuit works on the transmitter and receiver side?

7) I've checked the length of the strap and I was able to verify that a regular cleaning improve the transmission and low down the interference level? why?

8) How is the transmitter ?receiver encrypted? Is it the ASK code? or other ?

9) Is there a HRM which can download directly its data to a laptop through the infrared port? Guy (gnh888)
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gnh888
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Answers:

  1. The HRM transmitter needs moisture on the electrodes to make a good electrical connection with your chest, where it picks up the small EKG signal from your heart.

  1. I guess that the grooves are to hold the moisture in place by surface tension.

  2. Polar's website doesn't mention the details of the wireless link. The antenna may be a small loop similar to those used in pagers. Check this:

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  1. I guess that the length of the wings was chosen to pick up the best EKG signal.

  1. The heart's signal is detected by current conduction directly throught the chest. It is then converted to wireless by the transmitter.

  2. No info.

  1. Cleaning the strap improves the electrical connection to your heart and reduces EM interference from other sources such as power lines - it should not affect the wireless transmission or reception.

8 & 9. No info.

-- Joe Legris

Reply to
jalegris
5.> Is it by induction?

google around--- ECG-Amplifier.

The simple ones uses a 3 kHz oszillator that is triggered once a heartbeat (QRS-Complex. See slaa280 by ti.com. There is a little overview about ECG and signal processing. But be careful, there is a lot of garbage in it too ;-)

Your Skin (everyones) produce fat to save the surface. Fat doesn't conduct well so remove this will improve the contact, cleaning the skin too.

Newer system use multiple pulses per QRS-complex. They are coded to separate pulses from several systems.

Don't know. I saw a schematic few years ago, one guy uses Soundcard as interface with a simple 3 kHz LC-Antenna

Marte

Reply to
Marte Schwarz

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