2 channel ECG aquisition

[jbot2222]

Hi,

I am attemption to acquire an ECG signal from two sources using the following code. I'm having two problems with the situation:
1. I cannot get a simultaneous signal from my card. The card is a NI 6062E.
2. The signal I do get is accurate for a few seconds, after which it saturates to 5 or 10V.

I checked the card under Measurement and Automation Explorer, and monitored the signal through the Test panel. I got a clean signal there, but the signal continues to saturate in the VI...

any thoughts?

[Daddy-O]

I'm kind of a newbie, and I am sure people will chime in and correct me, but this should get the ball rolling!

I have a similar application, but 36 channels simultaneously. What I had to do is build a task with multiple channels, and read them in the same measurement. SInce it seems you are doing exactly the same thing in both loops it should be "simple" by LabVIEW standards. I have atttached my sample, maybe you can make a 2 channel task that builds an array. I hope this starts you in the right direction, at the very least, I am sure you will get info from others criticism of it!! LOL

Remember to build a task with both channels in it.

Chris

[jbot2222]

Chris - Thanks for your help with the problem! Our labview wont let me open your program because it seems to be saved in version 8.2 of the software, whereas I have version 8.0 Any way for you to save and repost in the previous version?

[Daddy-O]

I don't have 8.0 but I "saved for previous version". Since I don't have 8.0, I can't tell if it took.

Let me know if it worked...

Chris

Also, here's a screenshot

[Hani R]

Hi jbot2222,

The reason you are not able to acquire two analog input channels is because you are creating two analog input tasks.  You should get rid of the second task and look under the LabVIEW Help (search for Physical Channel Syntax) to get a better understanding on how to setup a single task with multiple inputs. 

As for the voltage saturating at 5 or 10V, you may have an issue with grounding.  Refer to the Developer Zone article: Field Wiring and Noise Considerations for Analog Signals for details about how you should be measuring your signal.  The important questions to answer are what input configuration are you using (differential or referenced single ended) and is your signal source a floating source (not connected to building ground).  For example, if your signal source is floating and you want a differential measurement, you will need to connect bias resistors from the input channels to ground.

Let us know if you have any other questions. 

[jbot2222]

So, I was able to get two signals from the suggestions above. Now I'm wondering how I can save the two signals in one file without having to merge the signals into one.

Any suggestions?

[Dennis_Knutson]

They are being save in one file. You have an array of waveforms and each channel is in a different column in the series of lvm files you write.

[dbmgeo]

Please tell me if this VI can be modified so that I would be able to use it with a Labjack U3.

Thanks a lot

[Hani R]

Hi dbmgeo,

I don't have any experience with LabJack but, from what I understand about the product, you can download the driver from the LabJack website to be able to use LabVIEW with the device.  If you are using the LabJack device then you will probably need to modify any code that uses the NI-DAQmx driver.  You may be able to find detailed information on the LabJack website and support forums.