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need help

hi

m an undergraduate student..

my final year project is to display ecg with the help of labview...

plzzz help me out...

i used simulator and send ecg signal via sound card in labview. should i place an amplifier circuitry in between simulator and sound card? which amplifier?

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Message 1 of 29
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Most ECG simulators have a low-voltage output that mimics the actual signal that is present on the human body (approx. 1mV peak).  Your sound card may be sensitive enough to pick this signal up on the microphone input (definitely not on the "line" input), but even if it is sensitive enough, the sound card's high-pass input filter (it probably has a DC-blocking series capacitor) may overly distort the ECG signal since audio is generally cut-off below 20Hz. 

Your best best is to build a simple instrumentation amplifier (there are many examples - just Google for ECG amplifier, biopotential amplifier, biosignal amplifier, etc.) and use this to amplify the output from the simulator.  Once you get a clean output signal in the range of 1Vpp, then run this into low-cost DAQ board (like the NI USB-6008).  Since you are only using a simulator, you will not need to worry about safety/isolation, etc.  Just don't use this setup on any humans!

Good luck!

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Message 2 of 29
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hi

i dnt know what do u mean by ECG simultor is it a device ??

anyway as far as i know any ECG project have to use instrument amplifier i can recommand you to google AD620


you will find many examples realted to what you want to do

any further question feel free 2 ask

hint: i am a student and i am working on the same idea but i have to send the ECG signal using bluetooth

good luck 2 all

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Message 3 of 29
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I can confirm that sound cards do have low frequency cut off around 10Hz and they are indeed AC coupled. You can use a sound card, if you do not have anything else. But your ECG wave form will not have the low frequency information. However if you are just using it for heartbeat calculations a sound card should do just fine. And as Steve indicated, Google is an excellent source for circuits. For using your ECG simulator I would recommend reading the manual. But most ECG simulators are made so you just hook it up instead of patient.



Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
(Sorry no Labview "brag list" so far)
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Message 4 of 29
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simulator is basically an artifi

cial patient, producing ecg waves... its a machine.

thnx every1:) i placed simulator lead in sound card, only the wave is not there, else waves r coming...

i used an example program..named as continous wave... this program gave me the ecg wave but t wave is absent:(...

i will place the instrumentational amplifier as soon as possible...

i need all of u help in signal processing of ecg..

take care u all.

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Message 5 of 29
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The reason that you only see the R wave is because this wave has the fastest rise/fall times and therefore the highest-frequency components.  The P and T waves are lower frequency are being blocked by the high-pass filter of the sound card.  The R wave (or part of it) is making it through, but it is probably somewhat distorted.  As Coqrouge says, it is probably good enough if you are just trying to determine heart rate.  If you need to see the true ECG waveform from the simulator, you need to replace the sound card with a data acquisition device (and preamplifier) that has a wider input bandwidth - something like 0.1-0.5Hz high-pass filter will be good for ECG.  The upper (low-pass) filter can be 100Hz or so.

Why is ECG not recorded with DC inputs?  Mainly because the electrodes used to acquire ECG generate a DC offset that is not exactly the same on each electrode resulting in a differential DC signal.  This DC signal will offset the actual ECG waveform up/down and this offset can be great enough to block (saturate) the instrumentation amplifier.  Worse, this offset is very sensitive to movement of the electrodes and other factors, so the DC offset drifts around causing the ECG waveform to wander up and down.  An AC coupled amplifier blocks this DC (or near DC) signal which keeps the ECG signal centered in the instrumentation amplifiers range.  A secondary benefit is that an AC coupled amplifier can be inherently safer since DC fault currents originating from the active components in the amplifier (power supplies, op-amps, etc.) cannot make it to the patient, making some AC-coupled amplifiers almost as safe as truly isolated amplifiers.

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Message 6 of 29
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You can use a simple mixer to up-shift the ECG waveform to a center frequency within the passband of the sound card, but you may get signal distortion.

A nice, inexpensive, really good ECG amp is the INA122P.

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Message 7 of 29
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my ECG signal is in lab view now:)

now i want that i get the value of voltage and time at each and every point...

like for example p wave i want the voltage of p wave at each and every point...

what should i do next.?????

this all i have to do in labview..

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Message 8 of 29
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How is it that you want to see the time/voltage pairs? graph? a table?

If you post your VI or a screenshot of your code it will make it easier for us to see the current type of the data so that we can help you display it in the format that you need.

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Message 9 of 29
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hi

now m working on 12 lead ecg...

(1) can any one send the theory literature on this?

(2) i thought that i will use instrumentational amplifier, will amplify each lead signal (means have to place 12 ins.amp) then each o/p will go into the mux, in mux selection lines the address will be coming from parallel port so that which lead should be select, and then selected data will go from o/p port to pc via sound card... is this possible????????

(3)still some questions are in my mind but not clear enough!!!!!!!!!

like in 3 lead ecg, if we want to see the lead 3 o/p it means that its the combination of 2 lead or 2point...

how we will achieve this in my approach.... M V V V V V V CONFUSE PLZ HELP:(

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Message 10 of 29
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