Searching \ for 'Sensor for Pulse (Heart)' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: techref.massmind.org/techref/io/sensors.htm?key=sensor
Search entire site for: 'Sensor for Pulse (Heart)'.

Truncated match.
PICList Thread
'Sensor for Pulse (Heart)'
1998\03\28@104648 by Adi

flavicon
face
Hi!

Is there a reliable but easy to use method to pick-up someones
pulse?

Regards,
Adi

1998\03\28@105310 by Walter Banks

picon face
Most of the sensors I have seen measure the IR transmission through some
soft tissue
like the end of a finger. With minimal hardware and software processing the
pulse is readily detected.


Walter Banks

> Is there a reliable but easy to use method to pick-up someones
> pulse?

1998\03\28@182404 by Don McKenzie

flavicon
face
Adi wrote:
> Is there a reliable but easy to use method to pick-up someones
> pulse? Regards, Adi

Yes, jump on his foot, that will pick it up somewhat!
Sorry, couldn't resist. :-)

Listen to Walter. His method is more reliable and logical.

Don McKenzie  spam_OUTdonTakeThisOuTspamdontronics.com   http://www.dontronics.com

Don's Download Dungeon http://www.dontronics.com/download.html
For more details, send a blank message to .....infoKILLspamspam@spam@dontronics.com
or simstickspamKILLspamdontronics.com or .....basicsKILLspamspam.....dontronics.com

1998\03\29@005206 by Mike Ghormley

flavicon
face
Adi wrote:

> Is there a reliable but easy to use method to pick-up someones pulse?

My admittedly limited knowledge is that they are using either an IR
emitter on one side of the finger (or earlob) clip and an IR detector on
the other side, or an emitter/detector pair on just one side.  At any rate,
whether detecting the IR through or bounced, they look for variations in
the IR level to detect pulse.

This is at least true in the two aerobic machines that I have collecting
dust in my garage, as well as the local doctor's office and ER room that I
visited recently.

Michael

*****************************************
The strong do what they have to do and
the weak accept what they have to accept.
                            --Thucydides

1998\03\30@050542 by paulb

flavicon
face
Mike Ghormley wrote:

> My admittedly limited knowledge is that they are using either an IR
> emitter on one side of the finger (or earlob) clip and an IR detector
> on the other side, or an emitter/detector pair on just one side.

 And others wrote similar.

 Actually, early machines used an incandescent lamp and may have been
sensitive to IR.  I suspect if you watch most of the current ones, which
use LEDs as the light source, you will notice that you can *see* the
light; thus it is *not* IR.

 There is one more trick however.  The LED in most medical systems is
actually two in inverse parallel, driven by an alternating voltage (with
one or more "off" phases).  Not only does this allow rejection of
ambient light, but the two wavelengths used are "tuned" to the
saturation spectrum of haemoglobin and used thereby to indicate oxygen
saturation, something usually of great concern when a patient is
monitored.

 One other thing.  The design of a clip to monitor the finger is non-
trivial.  Ear-clips are easier because the earlobe doesn't move itself!

 Cheers,
       Paul B.


'Sensor for Pulse (Heart)'
1998\04\01@120331 by Josef Hanzal
flavicon
face
Hi Paul,

this sounds very interesting, do you know any more details about the oxygen
saturation measurement? Perhaps wavelengths, source of coupled LEDs or
finger/ear subassemblies, anything, which would help building such a sensor?
TIA.

Josef

>  There is one more trick however.  The LED in most medical systems is
>actually two in inverse parallel, driven by an alternating voltage (with
>one or more "off" phases).  Not only does this allow rejection of
>ambient light, but the two wavelengths used are "tuned" to the
>saturation spectrum of haemoglobin and used thereby to indicate oxygen
>saturation, something usually of great concern when a patient is
>monitored.

1998\04\01@123713 by ogerio Odriozola

flavicon
face
Hi Josef,
    you could try your local hospital or medical supply house. Most are
using disposable led sensors, think they charged me about $8.00 US dollars
for one last year (thats hospital price, not supplier which must be much
cheaper). Kept it to play with it later but can't find it   : - (

Rogerio





EraseMEeuroclassspam_OUTspamTakeThisOuTPHA.PVTNET.CZ on 01/04/98 11:03:44 AM

Please respond to PICLISTspamspam_OUTMITVMA.MIT.EDU

To:   @spam@PICLISTKILLspamspamMITVMA.MIT.EDU
cc:    (bcc: Rogerio Odriozola/MTY/TVA/Dataflux)
Subject:  Re: Sensor for Pulse (Heart)




Hi Paul,
this sounds very interesting, do you know any more details about the oxygen
saturation measurement? Perhaps wavelengths, source of coupled LEDs or
finger/ear subassemblies, anything, which would help building such a
sensor?
TIA.
Josef
>  There is one more trick however.  The LED in most medical systems is
>actually two in inverse parallel, driven by an alternating voltage (with
>one or more "off" phases).  Not only does this allow rejection of
>ambient light, but the two wavelengths used are "tuned" to the
>saturation spectrum of haemoglobin and used thereby to indicate oxygen
>saturation, something usually of great concern when a patient is
>monitored.

1998\04\02@035022 by Werner Terreblanche

flavicon
face
--
Werner Terreblanche  <KILLspamwterrebKILLspamspamplessey.co.za>Tel :  (021) 7102251 (office
hours)

{Quote hidden}

       Somewhere at home I have the complete circuit diagrams and
discription of a commercial Pulse Oximeter, such as the type they use in
operating theaters to measure the oxygin content of the patients blood.  I
also have a comprehensive article describing the working principles behind
such an instrument.  The only problem that I'm not sure where these papers
are at the moment. I recently moved house and have several huge boxes filled
with papers and junk waiting in my garage to be unpacked, and I fear these
papers are hidden somewhere amongst them.

       I can't remember the details but as far as I remember it worked
something like this...  You have a normal visible red LED and an Infrared
LED both shine through the earlobe (not pulsed, but with a constant current
flowing through them).  When the heart pumps you can distinguish between the
high and low parts of the graph due to more less blood flowing through the
earlobe.  A measurement is taken of in both the intesity of infrared and
visible spectrum light at the other side of the earlobe on the top
(heatbeat) and bottom part of this graph.  Because oxygin in the blood
affects the visible and infrared light differently, you can derive the
oxygin contents from the difference in readings from the peak and bottom of
the graph.  The visible light acts as a reference to cancel out the effect
from the strength of the heartbeat, and the infrared light is used for the
actual measurement.  There exists a specific formula to calculate all this,
but I must add that it is not trivial.   Not the typical Friday evening
project, if you know what I mean.

       I'll look around if I can find those articles and circuit diagrams,
but I can't promise anything...

       Rgds
       Werner

1998\04\02@201958 by Bob Fehrenbach

picon face
Werner Terreblanche <spamBeGonewterrebspamBeGonespamPLESSEY.COM> wrote:
>        I can't remember the details but as far as I remember it worked
>something like this...  You have a normal visible red LED and an Infrared
>LED both shine through the earlobe (not pulsed, but with a constant current
>flowing through them).

   I was involved in the design of a pulse oximeter several years
   ago - did the DSP routines used to filter the pulse waveforms.
   Our unit and, as far as I know, all commercially available units
   pulsed the LEDs.  Having both on at the same time would have required
   filters to distinguish the signals from the two LEDs.  This would
   have added to the cost of the sensor assembly which is often a
   disposable and quite cost sensitive.  Also, many of these units
   are battery operated and pulsing the LEDs lowers power consumption.

> The visible light acts as a reference to cancel out the effect
>from the strength of the heartbeat, and the infrared light is used for the
>actual measurement.  There exists a specific formula to calculate all this,
>but I must add that it is not trivial.

   Not only non-trivial but inadequate.  Conventional absorption
   equations are generally used to explain the theory of operation
   but in actual practice the non-linearities kill you.  For
   example, the math assumes a fixed optical path length but that
   varies with the pressure changes during the pulse as well as
   physical motion of the patient.

   Units that I am familiar with use tables of emperical data
   gathered on real live clinical volunteers.


>Not the typical Friday evening project, if you know what I mean.

   Amen to that!  We had a development team of three engineers
   and the project consumed *MANY* months.

--
Bob Fehrenbach    Wauwatosa, WI     TakeThisOuTbfehrenbEraseMEspamspam_OUTexecpc.com

1998\04\03@095909 by John Shreffler

flavicon
face
part 0 848 bytes
-----Original Message-----
From:   Bob Fehrenbach [SMTP:RemoveMEbfehrenbspamTakeThisOuTEXECPC.COM]
Sent:   Thursday, April 02, 1998 8:05 PM
To:     PICLISTEraseMEspam.....MITVMA.MIT.EDU
Subject:        Re: Sensor for Pulse (Heart)

Werner Terreblanche <EraseMEwterrebspamPLESSEY.COM> wrote:
>        I can't remember the details but as far as I remember it worked
>something like this...  You have a normal visible red LED and an Infrared
>LED both shine through the earlobe (not pulsed, but with a constant current
>flowing through them).

[John Shreffler]  There was a story on one of the network magazine
shows last week about marriage counciling, in which the couple was
put into a special room and hooked up to a lot of sensing and recording
equipment to measure stress, etc as they talked about their problems.
One of the sensors was a thing clipped onto the ear lobe.


1998\04\03@112100 by Harri Suomalainen

flavicon
face
>Werner Terreblanche <RemoveMEwterrebEraseMEspamEraseMEPLESSEY.COM> wrote:
>>        I can't remember the details but as far as I remember it worked
>>something like this...  You have a normal visible red LED and an
Infrared
>>LED both shine through the earlobe (not pulsed, but with a constant
current
>>flowing through them).

For pulse rate you can use visible led or infrared led combined with a
receiver
diode. Monitor the light passing to get pulse. As simple as that.

Visible led *and* IR led are needed for measuring oxygen content in
the blood stream. By comparing IR and visible light passage you can
determine oxygen content. Unfortunately you usually need a person
for calibration. Usual method for this is adding CO2 content of the air
to lower oxygen content in blood. Not a thing to do home.


--
Harri Suomalainen     RemoveMEhabaspam_OUTspamKILLspamcc.hut.fi

We have phone numbers, why'd we need IP-numbers? - a person in a bus

1998\04\04@153701 by paulb

flavicon
face
Josef Hanzal wrote:

> Hi Paul,
>
> this sounds very interesting, do you know any more details about the
> oxygen saturation measurement? Perhaps wavelengths, source of coupled
> LEDs or finger/ear subassemblies, anything, which would help building
> such a sensor? TIA.

 I daresay my answer is "no, I just watch the display"!  Which is
pretty close to the truth.

 I have a couple of PCB assemblies from one of those shopping-centre
"measure your pulse" units and occasionally I score a dead sensor but I
haven't scored the whole box yet (but it *could* happen!).

 My comments, or re-iteration thereof:

 1) Don't try and engineer the sensor.  Buy them ready-made.

 2) Of COURSE they use the two LEDs counter pulsed as I originally
described!  (Thanks Werner!)  Four wires plus shield.  How else?

 3) If you *must* make your own (electronics, not sensor), don't even
*dream* of using mathematical modelling.  Get some volunteers (find a
suitable range of specimens corresponding to those you expect to use it
on e.g. healthy, crook, decrepit etc...), make measurements, plot a few
curves and model those.

 4)  No, you do *not* vary CO2 to calibrate O2.  You vary O2 of course!
Not a problem, you just use a hospital with all the equipment already,
including an anaesthetic machine to dial up whatever O2 you like and
the instruments to verify the actual inspired O2.  For most purposes,
you would simply compare your prototype with another such instrument.
Only if you *really* are going into the competitive medical market are
you going to pay volunteers to have their arteries cannulated!

 Cheers,
       Paul B.

More... (looser matching)
- Last day of these posts
- In 1998 , 1999 only
- Today
- New search...