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'Electrocardiogram (PICECG?'
1999\03\27@100320 by Howard McGinnis

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In a paper found on the web from MIT Health Sciences and Technology, it was
stated that the electrocardiogram signal is approx 1 mv in amplitude. If
the signal is amplified, how can the 60 Hz be filtered by the PIC without
affecting the ECG signal?

Howard
Howard McGinnis
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1999\03\27@110416 by Ross Bencina

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Howard McGinnis writes:

>In a paper found on the web from MIT Health Sciences and Technology, it was
>stated that the electrocardiogram signal is approx 1 mv in amplitude. If
>the signal is amplified, how can the 60 Hz be filtered by the PIC without
>affecting the ECG signal?


This is a classic DSP application, infact I have a textbook here with an
example. They use a FIR filter of length 75 with a passband of 9 to 39 Hz,
sampling rate 500Hz. Then they perform other enhancement processing too.
It's more common to perform such processing with a DSP chip rather than a
microcontroller.

Digital Signal Processing - A Practical Approach. Emmanuel C. Ifeachor and
Barrie W. Jervis. Addison Wesley, 1993.

I'm not sure I would recommend this book though. You will probably find
similar examples in most University textbooks on DSP.

If you want to know more about filter theory, grab a book, or go talk to the
guys at comp.dsp

Ross B.

1999\03\27@234713 by Chris Eddy

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Um, don't take me for an expert, but I think that a few principles apply.
First, there is always a ground lead on the patient, usually an ankle strap.
This gives a ground reference on the patient and should help reject a lions
share of 60Hz.  The second is this.. Tread carefully when connecting up to
humans.  These machines are built with exceedingly complicated safety features
such that it is nearly impossible to have the circuit burn up and apply large
DC voltages and currents to the victim.  When you are scurely attached to the
person, and shocking him//her, it doesn't take much to kill.

Chris Eddy
Pioneer Microsystems, Inc.

Howard McGinnis wrote:

{Quote hidden}

1999\03\28@001002 by Gerhard Fiedler

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At 23:42 03/27/99 -0500, Chris Eddy wrote:
>DC voltages and currents to the victim.  When you are scurely attached to the
>person, and shocking him//her, it doesn't take much to kill.

IIRC, around 50mA is almost always deadly.

ge

1999\03\28@012057 by : Cassie Carstens

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> > In a paper found on the web from MIT Health Sciences and Technology, it was
> > stated that the electrocardiogram signal is approx 1 mv in amplitude. If
> > the signal is amplified, how can the 60 Hz be filtered by the PIC without
> > affecting the ECG signal?
> >
> > Howard
> > Howard McGinnis
Hi Howard
ECG power... MUST be isolated !!! (1,DC to DC converter 2, Optical
eg. convert amplified signal to drive HP optical isolators) Analogue filters
works fine.
Three pickups, one ground, placed across chest. Skin streach between
two pickups monitors breathing. (resistance)
Cautions: a few micro-amp can deflibilate the heart. Chemical burns
can occur under pad because of conductive gell. Hi frequency signal
(diathermy) or radio can turn ecg cables and pads into antena and
complete its path though skin.(bad burn)
Depending what you want to do, there are ecg interfaces (preamps)
available, You supply power and get signal. (insolated, CE app. safe
and $$$. If you want to do interface part....research and goooood
luck.
Regards
Cassie

1999\03\28@044448 by Steve Tomes

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At 08:33 AM 3/28/99 GMT+2, you wrote:
Don't know what your app is but might be easier to measure pulse with
presher sensor......

1999\03\28@104125 by Wagner Lipnharski

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Analog Devices has special chips for that purpose.

Gerhard Fiedler wrote:
>
> At 23:42 03/27/99 -0500, Chris Eddy wrote:
> >DC voltages and currents to the victim.  When you are scurely attached to the
> >person, and shocking him//her, it doesn't take much to kill.
>
> IIRC, around 50mA is almost always deadly.
>
> ge

1999\03\29@001017 by Sean Breheny

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At 10:39 AM 3/28/99 -0500, you wrote:
>Analog Devices has special chips for that purpose.
>
>Gerhard Fiedler wrote:
>>
>> At 23:42 03/27/99 -0500, Chris Eddy wrote:
>> >DC voltages and currents to the victim.  When you are scurely attached
to the
>> >person, and shocking him//her, it doesn't take much to kill.
>>
>> IIRC, around 50mA is almost always deadly.
>>
>> ge
>


Analog devices has special chips to source 50mA into people?! <BG>

Sean

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1999\03\29@024424 by Gerhard Fiedler

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At 00:08 03/29/99 -0500, Sean Breheny wrote:
>At 10:39 AM 3/28/99 -0500, you wrote:
>>Analog Devices has special chips for that purpose.
>>
>>Gerhard Fiedler wrote:
>>>
>>> At 23:42 03/27/99 -0500, Chris Eddy wrote:
>>> >DC voltages and currents to the victim.  When you are scurely attached
>to the
>>> >person, and shocking him//her, it doesn't take much to kill.
>>>
>>> IIRC, around 50mA is almost always deadly.
>
>Analog devices has special chips to source 50mA into people?! <BG>

do you need sources? :)

ge

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