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Dan Major
07-06-1999, 11:38 PM
We frequently run experiments or teaching labs where monitoring the
heartrate of subjects is important, either as data for the experiemnt or
for safety concerns. The first system we used was the typical 3-lead ECG
setup with a high gain differential amplifier and a biotachometer. The
signal from the biotach was then sent to an A/D board in a computer, and
displayed on the computer monitor and recorded on the hard drive. The
problem with this is that the cables interfere with upper body motion, and
can be something of a hazard. Additionally, there is some technique needed
to prep the skin prior to electrode placement, and modesty concerns usually
limit the subjects to males only.

The next thing we tried was the "system" sold by Polar. The system
consists of a transmitter which is attached to an elastic band, worn just
below the pectoral muscles. On the QRS complex, a radio-frequency signal
is sent to a receiver. The receivers can be in the form of a watch, a
bicycle speedometer, or a small rectangular unit.

The problem we're having is that the unit's performance is very erratic.
Sometimes it will display no heartrate, other times the heartrate is wildly
high. We've tried everything we can think of - varying position and
orientation, proximity to metal objects, proximity to computers and other
RF generating equipment, etc. Nothing has substantially improved the
performance and reliability.

I'd like to solicit opinions of the listers as to what they would recomend.
The main criteria are that the unit be easy to use by untrained
experimenters, be capable of transmitting the signal wirelessly with a
range of over 1 meter, must not substantially restrict motion, be mostly
immune to interference from external sources and not generate false
readings due to over-sensitivity to artifacts, and be affordable. If it
can also cook and do laundry, I might consider marrying it (grin). I
realize this is a lot to ask for, but surely some of you must be having the
same problems, and I'd like to hear what your solutions are. Thanks in
advance.
Dan Major
Univ. of Okla. School of Industrial Engineering
major@ou.edu htp://www.ecn.ou.edu/~major

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