how to record a signal in Labview ?

[bhavin2]

Hello friends,

I am working on ECG and I want to record it for atleast 2 min , so my colleage can see it again.
even let me know if we can get the data of time and amplitude so we can plot it out with help of excel or Matlab.

Regards,

Bhavin

[TroyK]

Yep it can be done. Could be A LOT of data over 2 mins. You can capture straight to a tdms file on the hard drive.

[devchander]

Bhavin,

Let us know how are you acquiring the ECG data

Are you using a DAQ card??

Reading data at some serial Port??

With this information, we could sugest a suitable file writing/saving method

regards,

Dev

[NetizenKane]

Could you also provide some information about your measurement properties like sampling rate and your number of channels?

Greets

Kane

Message Edited by NetizenKane on 05-21-2007 07:57 AM

[Herbert Engels]

Sounds like a poster child use case for TDMS files. Feel free to look into our online tutorial http://zone.ni.com/devzone/cda/tut/p/id/3539 and into some of the examples that ship with LabVIEW (in particular: "Cont Acq&Graph Voltage - Write Data to File (TDMS).vi").

The file format is documented (http://zone.ni.com/devzone/cda/tut/p/id/5696) and supported by LabVIEW, LabWindows/CVI, SignalExpress, DIAdem and Excel.

Hope that helps,
Herbert

[bhavin2]

Hello Mates,

This is a single channel ECG and I m using NI USB DAQ 6215 .
and I have kept the samoling rate at 1000 S/s.
Thanks you all for the nice info.

Bhavin

[devchander]

The information given by Herbert should help you to achieve what you are trying to do

[sadfjhas]

Hello mates,

Thanks for the help. but I could not find  the TDMS VIs and even I want to record my  signal in text form
so I can use it for other application and want to read it again. I also tried with write measurement data but could not save the singla more than .5 second as the data rate is 1000 S/s.

Please help me in the context.

Regards,

Bhavin

[Skydyvr]

How compact is a TDMS file? Or more specifically, how does it compare to just the standard binary file write? Whenever I need to stream data to a disk, I typically have large amounts of data (40kHz sampling for 15 minutes or more). TDMS sounds like a nice way to store data, but I can't afford very much overhead.

Thanks

[TroyK]

Skydyvr,

I've used tdms files to record 30 seconds of an 800KS/s signal. It worked perfectly.

It isn't compressed or anything, still writes binary data, just organises it nicely.

It does zip down very small if your worried about space. The links in Herbert's post explain it in detail.

Sadfjhas,

Couldn't tell you why you can't save more than 500ms unless you attach your vi so we can have a look at it.

Saving the data as a text/csv file is very inefficient (One byte for every character can easily triple the size of your measurement file). What other application do you want to read the captured data in? 2mins of 1KS/s data is 120000 points of data, if you want to open it in Excel for example, you have a problem. Excel will only display 65536 points of data.

Regards,

Troy

Message Edited by Troy K on 10-18-2007 05:08 PM