Re: pulse sensor I need help with

Robert Wechsler (
Mon, 05 Apr 1999 12:56:06 +0200

Aaron Davidson,

my dance company has been performing dances for some time which use the
beat of the heart to set the rhythm of musics, play a beat, determine
graphics, etc.

i can tell you a little about our experiences:

we also began by looking at such IR medical sensor equipment. they are
extrememly sensitive, and also reveal info about blood oxygen levels for
example, which is quite fun. the problem we encountered was that they are
also sensitive to vibrations, shaking etc. making them pretty useless for
dance applications.

we next looked at microphone systems. Siemens for example, makes (and lent
us) some quite cool microphones. but in practice, same problem, the
background sounds were too great.

Next we looked into electrodes, since, as the medical experts had told us,
the heart beat is actually a very powerful electrical signal. With the
proper software filters this turned out to work pretty well. A fellow
working with us suggested we simply use a Polar-brand athlete's heatbeat
sensor. In those days they were very new and we had to write to Finnland
to get them, but I believe in the meantime they are available at any sports
store, fitness gyms etc.

Polar includes built-in filter circuitry, and are quite reliable, even
while dancing. They send a low-radio frequency "pulse" which can be picked
up by a simple induction coil. We built little amplifiers which turn the
polar signal into a strong audio "pulse" which we then input to standard
microphone (or electric guitar) wireless transmitters.

I or my partner, Frieder Weiß, can go into more detail about how we did it,
indeed, we can even sell you a complete system ready to use. (see

Some tips for their use:

1 put a little spit on the electrode part of the belt before putting it
on. better still, use a little electrode gel (hair gel can work too, but
check its conductivity first. you can add a little salt if necessary).
2 put the polar units on at least 15 min before going on stage. they warm
3 use the belt pretty tight.
4 clean the belt with soap and water after use. sweat will eventually
corrupt their conductivity.

- - - - - - - - - -

Heart beats, by the way, are quite interesting things. The sound of them
can be soothing, or tension-building. They have long and short-term
respiratory cycles (separate from the activities we are performing). They
can be more or less "rhythmic" depending on various factors.

They respond to virtually everything we do, and yet, one can learn, in a
concentrated moment, to influence them. That is, they are not necessarily
beyond our control. Perhaps most interesting to me as an artist, however,
is that they tell something about what a person is experiencing (as opposed
to what they want us to see). That is, they reveal a truth about us which
is normally hidden. (now if that is not art... ).

Hope this is helpful.


At 08:17 PM 3/15/99 -0700, you wrote:
>Hello- I have a COMBI pulse sensor (clip on ear?) I stumbled across, no
>packaging or info, just the sensor (IR emitter/detector ?) that terminates
>in a 1/8 inch stereo plug. The only electronics are the emitter/detector,
>one on each side of the clip.I had hoped to interface this with the
>sensorlab/i-cube. I honestly am not sure of the operation of these sensors
>(pulsing of blood obstructing Infra Red emitter, detector registers change
>in IR transmission through ear lob?).
> (snip)
>any and all advice will be greatly appreciated,
>aaron davidson