ECG Data Acquisition

[Himanshu]

Hello LabVIEW Users,
I am trying to acquire ECG signal using a CONTONIUS ANALOG SINGLE CHANNEL INPUT VI in LabVIEW. I would like to know that will I be able to acquire the ECG waveform using this VI or will I need a CRO for this purpose I have not considered CRO because I understand that the heart beats at the rate of 96 beats / min so the signal is very slow varying. If you agree that the ECG can be acquired using the above mentioned VI then I would like to know about the scan rate which will be fit to do so. I must also tell you that the sampling rate for ECG is 300 samples / sec. So it would be nice if some one could please tell me about which VI will be perfect for acquiring the ECG

[Christopher Mitchell]

hhjjj --

Don't know what a CRO is but I will try my best to answer your question. Two things to consider when acquireing an ECG signal: 1. Resolution and 2. Sample Rate.

1. The output from standard ECG leads is in the milliVolt range (~1 to 3 if i remember correctly). The smallest voltage change the average NI data acquisition board will be able to detect is ~1 milliVolt. So, you will have to amplify and filter the signal from the leads to have a good enough signal to visualize in your VI.

2. The peak Hz in a ECG signal, the QRS complex, is around 17 Hz (again, my memory is a little fuzzy here) so, theoretically, you can sample data around ~34 samples/sec and get away with it. However, I would recommend a x10 sampling rate (~170 Hz). 300 sample
s/sec should be fine but don't oversample or you will introduce unwanted noise in your signal.

So, I think the VI you are using to display the ECQ signal should be fine. But, I think an emphasis should be placed on how you acquire the signal.

Hope this helps.

[Himanshu]

Dear Sir,

Thanks for you reply, As far as I know the sampling rate of the PCI 6023 is constant. I would like to know of the SCAN RATE which I have to give in the VI for acquiring the data. Please tell me what the scan rate is and how scan rate works.

How can we change the sampling rate from the front panel of the VI.
PLEASE TELL ME THE CONNECTION BETWEEN SCAN RATE AND SAMPLING RATE.

THANKS

[golubovski]

Don't know what CRO is, but you DEFINITELY need an amplifier cap[able of involving LP/BP filter at about 40Hz to eliminate the baseline wander (originating from muscle's EMG), and a net filter 50/60Hz. Sampling rate of 300Hz is OK, but I'd still do it in at least 500Hz as there is a significant morphology you might want to "catch". Normal HR is 70bpm not 96, and HR above 120 are considered to be fast (tachycardias/-arrhytmias) so some of the normal morphology is distorted. Build you own VI according the circumstances. Such sampling rates under 1kHz are really no problem to present on-the-fly while processing!

[Himanshu]

Dear friends,
A CRO is a Oscilloscope, which is given in the examples section of LabVIEW. What I want to know is that I am using CONTINOUS SINGLE CHANNEL ANALOG INPUT .vi for the ECG data acquisition I am unable to decide what SCAN RATE I should keep so that the ECG data get acquired. So my first requirement is the scan rate which I should keep? Further I want to know how scan rate is related to the sampling rate?
I would also like to know is the single channel oscillooscope can be used for ECG data acquisition because I feel that Oscilloscope id ment for fast varying signal where as the ECG is very slow.

[golubovski]

I guess scan rate and sample rate are same thing. Your sampling rate of 300Hz is sufficient for standard resting/holter applications. I use minimum 500Hz to be sure I get all details in the morphology. Anyway, since this becomes discussion, i recommend you post this topic on the info-labview forum (after you register with the list maintener of course). Doing this via WEB is really annoying for me!

[Scott Seidman]

golubovski wrote in news:506500000005000000D5E50000-
1042324653000@exchange.ni.com:

> I guess scan rate and sample rate are same thing. Your sampling rate
> of 300Hz is sufficient for standard resting/holter applications. I use
> minimum 500Hz to be sure I get all details in the morphology. Anyway,
> since this becomes discussion, i recommend you post this topic on the
> info-labview forum (after you register with the list maintener of
> course). Doing this via WEB is really annoying for me!
>

There is a usenet portal for this board: comp.lang.labview



--
Scott
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