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Question regarding ECG????????? plz help

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satyajit.mittra

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I see a lot of circuits in this community my question is if I make one of them and convert the analog output into digital, what exactly does the digital output look like is it the same for say two different people or is there a difference. Also say for example a person is stressed will the stress get reflected when the ECG signal is converted into digital. I am looking for finding a way to identify stress from the digital signal. IS it possible? Plz help thanks in advance
 

albbg

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An analog signal can assume an infinite number of voltage level. Due to this is not possible to send it directly to a microprocessor (or to a DSP) to eleaborate it.
These devices (as all the digital devices) operate on digital numbers that can assume a finite number of voltage levels (1bit=2 levels, 2bits=4levels, 3bits=8 levels...).
So if you take an analog signal and convert it to digital, the two will be almost identical. "Almost" because reducing the number of levels you will loose something of the original analog signal, but choosing a correct number of bits to represent the signal, you will loose a negligible part of information.
So, assuming your analog signal is properly sampled (not only in terms of bits, but also as sampling frequency and antialias filtering), you will have an accurate digital copy of it, ready to be elaborated.
 

karesz

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Hi satyajit,
If you will digitalize some (pulse) signal i.e. with 12 bit coverters; it means that your origin is up to ca. 0.01% is to find in the "collection of bits"...
These is a very fine resolution, but if only10 bits exact is the digital convrsion; you will a digital signal have what up to 0.1% the same is as the original!
I dont know what kind of precision stress analyzis needs, I can assume that at 1% will be OK, that is after digitalizing so 10...50 or 100x better.:)
CG Front-End Design is Simplified with MicroConverter®, www.analog.com/library/analogDialogue/archives/37-11/ecg.pdf
K.

Added after 3 minutes:

Here is a script over very high resolution ECG solutions: What are the advantages of a 24 bit system? www.biosemi.com/faq/24bitsystem.htm
Personal ECG Monitor(some discussion over signal processing): www.freescale.com/webapp/sps/site/a...5B9044BEGwt1&code=APLPECGMON&tab=In-Depth_Tab
 

satyajit.mittra

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thank you everybody I c wht you all mean I guess i'll have to figure out a way to process the signal to gather the required information. Thank you all gr8 help.
 

karesz

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:) welcome!
These is surly a main SW & dataprocessing problem-job...
Front-end electronics to become or build it self, is not the bigest problem_nowaday!
Good luck!
K.
 

satyajit.mittra

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thanks Karesz
btw do you by any chance know any good websites or books that can be useful for this purpose i.e. dataprocessing n all?
 

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