How to generate a bipolar pulse train in LabView using USB DAQ 6211?

[spamjam]

Hi,

I am setting up a system to generate either a single square pulse or a train of square pulses using LabView, with controls to adjust the frequency, amplitude, number of pulses etc. I have had a lot of help from NI tech support setting up the actual VI itself which seems to be working fine, and outputting the pulses via a USB DAQ 6211 using a square waveform generator and the AO1 channel on the DAQ.

The problem that I now have is that I need to pulses generated in a train to be bipolar (as they are connected to electrodes so need to be bipolar o avoid salt build up on the electrodes from the voltage going in one direction only, at least that is how I understand it!).

How can I set up my LabView VI to generate a bipolar pulse train instead of always being positive voltage? I am new to this area and so am trying to learn but there is so much to learn!

Thanks,

spamjam

[ShalB]

Hello spamjam.

Thank you for your post on the National Instruments forum.

Can you please post your code so that we can modify the existing program and implement what you are now trying to do.

Regards,

[spamjam]

Thanks, I will tryto do that.

Do I just copy the .vi file from my computer and attach it to the post using the attachments link at the bottom here? 

I will put itup as soon as I can, 

Thanks, 

[spamjam]

OK here is the VI we're using for the stimulation. If anyone has any suggestions for generating a bipolar pulse that would be great! 🙂

Spamjam

[ShalB]

Hi spamjam,

I have had a look at your VI and have run it as well. The graph that is displayed is bipolar. It has both a positive and a negative value already. For example if I set the amplitude to 10, I get a peak to peak value of 20 (from 10 to -10). Are you saying that you are getting only positive values on your graph?

Can you give me some more details on what you want to achieve?

Thanks,

[spamjam]

Hi Shalini,

Apologies for taking a while to get back to you, I hope I can explain what it is that we need to create with the pulses. I understand what you mean about the existing pulses having a positive and negative on the graph - but we need the pulses to start from a resting voltage and the first pulse to be positive, then back to zero, then the second pulse to be negative then back to zero etc. This is to do with reversing the direction of the current between two electrodes to prevent build up of salts on one electrod from the current always passing in the same direction. 

I have attached a .Tif file to this post to try to illustrate what I mean - the top picture shows how the pulses are currently generated, then bottom on is what we would like to produce if this is possible?

Thanks for your help,

Spamjam