Analog Output Buffer Size

[MSATLAB]

Hello,

     I have been running into problems with buffers lately and I can not seem to figure then out no matter what I read or see.  I have an analog output that I am sending a 0-10 volt signal out of.  I want to do it at 1k Hz.  I do not understand the buffer size on the terms of the output.  I get an error saying that the buffer size is 1 and it needs to be at least 2.  I could change it in my DAQ Assist to 10000 and it does not make a difference.  it still says that it is one.  So I don't know if I am just going about this the wrong way or what but help would be greatly appreciated.  If you need anymore information let me know! Thank you!

Michael B

LabVIEW 8.5

[RavensFan]

An obvious question would be what hardware are you using?  Are you using DAQmx or older Nidaq drivers?  Can you post the code in case the problem is a software issue rather than hardware?

[MSATLAB]

Hello,

     Thank you for the response.  I am using a USB-6259 DAQ.  The VI itself is very simple.  I am going from a DAQ Assist block to a indicator.  When I do this with custom DAQ blocks and not the assist block it works, but as soon as I exchange the blocks for the DAQ Assist, that is when things go haywire (I am personally exchanging them, not using the generate code feature when you right click).  I am assuming that I am using DAQmx as the drivers considering I am using a relatively new DAQ board and LabVIEW 8.5 was just installed on the system.  I just do not understand why my custom code for taking in continuous data works and the DAQ Assist doesn't even though I do not change the buffer size of each.  Thank you for your help again.

Michael B

[Yardov]

Hello Michael,

Is there a reason why you do not want to use the auto-generate code?
Without looking exactly what you are doing or the exact error code, I would assume is your timing settings. What type of signal datatype are you trying to output? Array, waveform or single value?
Is your ultimate goal is to have it on the DAQ assistant or on low level VIs?
There is a great tutorial about the DAQ assistant here that will help you with the terminology. Finally, there is an online video of how to create an analog output task here.
These material is part of the Getting Started with DAQmx which is a great resource center feel free to use it.
Finally, if you want, post a couple of images of the sections are not working for you, that works better for multiple LabVIEW versions users.
Hope this helps,

[MSATLAB]

Hello,

     Late last night I have figured out what I was doing.  I didn't have a chance to post on the wall with what I have found out.  I was just sending a single double to the DAQ Assist block and I guess that isnot what it wants.  I just wanted a constant voltage sent to the block so I thought that a number would be sufficient.  Obviously not.  I then put a simulate DC signal in front of that and I am adjusting the offset and sending it to my DAQ block, thus making what I wanted to in the begining with more than a standard number.  I guess it is the case of the Dynamic Data Type again.  So I seem to have fallen to it yet again.  Thanks for the help.

Michael B

[Yardov]

Hi Michael,

You are correct. For a single value output, you should do the following:

The important key fact here is not to use timing. This VI will tell the card that you will output multiple samples.

Good luck,


Message Edited by Yardov on 11-20-2007 11:02 AM