BNC-2120 Analog Output randomly stop working

[gwing]

I have a BNC-2120 Module. I have the analog outputs set up with a DAQ Assist. I am running a Square wave or Triangle wave at a very slow rate (.35 Hertz). I am monitoring the signals with a Waveform Chart just before they go into the DAQ Assist modules. The system runs fine from anywhere from a couple of minutes to 25 minutes. The outputs appear to just stop working but I can still see the signal on the Waveform Chart screen. I am thinking that the BNC-2120 module is having issues. Has anyone had a problem where the output just stop working? What can I look for in my VI program?

[kellis.wiseman]

What do you mean stop working? Is it flat-lining on the Waveform Chart, or does the Waveform Chart just go blank? Can you run a simple task in Measurement & Automation Explorer for more than 25 minutes without getting a strange signal? 

~kgarrett

[gwing]

The Waveform can still be seen on the Waveform Chart Screen inside Labview. However when I look at the signal at the output with an Oscilloscope it is flat lined. Stopping Labview or the simulation and restarting it resets some thing and I can see the signal again at the output for a period of time than it flat lines again. I have gone back to an old old file and it ran for 2 hours. Not sure I ran the old file long enough but it ran longer than my new VI. Is it the new VI or the something else. ????? I hope to know more soon.

[JVP · Accepted solution]

Hi gwing,

There could be a few possibilities that could be going wrong. Would you mind uploading your code? What DAQ device are you using with the BNC 2120?

Best Regards,

Jignesh

[gwing]

I have been able to narrow the failure down to a piece of my block diagram. The BNC-2120 seems to be working with older VI projects or block diagrams. I have included the VI in this posting. It could be the DAQ Assistant or the Shift Register that is causing the Problem. Anyone who can shed some light on the problem would be much appreciated.

Greg Wing

[NIquist]

There is nothing in your attached code other than two simulated signal generators.  Where is the DAQ code? What actual DAQ are you using?  Forget about the BNC-2120 being the issue.  It does have some active circuitry inside but not for the DAQ I/O.  The output from your DAQ card is just passing through that box.  It's nothing more than a convenient set of BNC jacks. 

BTW, You shouldn't have marked this thread as solved unless your issue is resolved.  Many people skip over solved threads.

[NIquist]

EDIT:  Oops, double-clicked. 

[gwing]

I am not sure why the DAQ's didn't show up. I will attach the file again. I am using Labview 7.1. I don't remember closing the file, sorry about that.

[gwing]

Please disregard the previous VI. Use this VI

[Dennis_Knutson]

I don't know what the problem is but your DAQ Assistants are not showing any channels.They are also set for single sample which would seem to be wrong if you want to output a waveform.

Why have you not provided the necessary information about the actual DAQ device you are using? That is essential information.

You should also be aware that if you set your output for a waveform, you simply cannot use two separate DAQ Assistants. You need to use one that is configured for 2 channels.