Ask how to open some files

[M0906961]

Thank you very much for your help. I will test my experiment first. If I have any questions, I would like to ask you again.

[altenbach]

I already poste a link to these files long ago, If the files are public, they should never be attached again, zipped or not.

This was an interesting problem and I was happy to play around, especially since I have a personal ECG monitor where I could not yet correctly reverse engineer the binary format for my own analysis in LabVIEW 😞

I am sure your use is educational and not commercial. It is an interesting project to analyze and compare all these pathological ecg sample traces.

I did not even look at the other three file type (not *.dat files), because they are very small. They might just contain metadata (e.g. time-base, recording date, formatting, etc.). The *.dat file contains the recording and is probably all you really need.

Maybe somebody could look at the MATLAB tools I linked earlier to see what they do. I don't "do" text programming and did not even bother.

Still, I recommend to start with the basic LabVIEW tutorial and especially learn about the various numeric representations. In this particular case, reverse engineering was relatively easy. If we just graph the raw U8 data, there is a periodicity of three, indicating 24bit data. (3bytes/point) After that there are only two possibilities for byte order (big vs little endian) and two possibilities (signed vs. unsigned integer). Harder was figuring out the wrapping, and there might be other ways to unwrap, but my solution seems to work fine.

[NIquist]

According to this How to use LabVIEW Biomedical Toolkit - ECG Feature Extractor (Ver 2012 ) - NI Community The LabVIEW Biomedical toolkit can open the MIT-BIH files.

I have played around with the toolkit, but I'm no expert on it.  I do know I had to get the Advanced Signal Processing Toolkit installed to make it work.  I have the 2019 Pro Dev LabVIEW and have the needed license.  There is a generous trial period if you want to check it out, but don't have the license.  Make sure you choose your LabVIEW version and 32/64 bit options correctly!

LabVIEW Advanced Signal Processing Toolkit Download - NI

LabVIEW Biomedical Toolkit Download - NI

[M0906961]

Thank you, I understand

[M0906961]

Thank you for your understanding and help. It is indeed for educational purposes. This is my own experimental topic. Thank you.

[M0906961]

Hello, expert. I would like to ask what is the unit of the Y axis (Amplitude) in the figure. If I want to display mV, is it possible? Where should I correct it in the program?

Thank you.

[altenbach]

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@M0906961 wrote:

Hello, expert. I would like to ask what is the unit of the Y axis (Amplitude) in the figure. If I want to display mV, is it possible?

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There are no "units", the are just raw integers based on the bit depth of the A/D converter.. In order to convert to millivolts, you need to know the instrument settings.

Typically, there is a linear relation and you can either apply the scaling to the values using simple math. If you just want the Y axis cosmetically in mV, you can set (y0,dy) of the Y scale.

[Bob_Schor]

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@altenbach wrote:

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There are no "units", the are just raw integers based on the bit depth of the A/D converter.. In order to convert to millivolts, you need to know the instrument settings.

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Counter-example:  I once worked with some BME graduate students interested in building an instrument that could be used in the Operating Room to judge (and quantify) emergence from the effects of paralytic agents after surgery.  The test was called a "Train of 4" -- a mild train of 4 pulses was applied somewhere (like the forehead) and the anesthesiologist rated them on a scale of (I forget, now, but something like) 1 to 5.  The idea was to replace the subjective "observation of forehead twiches" with measurements of skin movements, transduced by a small 3-D accelerometer (quite inexpensive).

Problem was the gadget was "unclaibrated".  The axes were well-aligned (90 deg between pairs), but gain (in v/g and offset (in v) had numbers like "Bias = 2.0 v ± 0.3 v" with similar wild values for gain.  I tried to get them "interested" in dealing with this issue, but they'd apparently never heard of Calibration, nor had any idea how to design a calibrator for this little 3-D acceleromter.  "Where would we get the precision stimulator?"

Sigh.  Put the accelerometer on a table top.  Assuming noone is hammering on the table, and you're not in the middle of an earth-quake, it is accelerating 1g in the vertical direction (Up?  Down?  we don't really care, as long as we are consistent).  Flip it over, make another measurement, and you have two equations in two unknowns, which they could solve.

But what about the other axes?  OK, turn it 90 deg along one horizontal axis, measure, invert, measure, now repeat with the perpendicular horizontal axis, and 2 measurements.  You now have 6 (not-carefully-measured, but roughly orthogonal) positions and 6 unknowns.  This problem is a little harder (I used the Simplex method, which I originally coded many years ago in Pascal, and simply translated to LabVIEW) and in a blink, I had bias/gain pairs that I could put into DAQmx to make the three axes output their values in units of "g" (I did it, of course, using the programming language "G", LabVIEW).

Bob Schor