DAQmx generated signal is not continuous

[jLeschke]

Hello,

 I have a question affecting the DAQmx functions in combination with LabVIEW RT. I'm using the DAQmx write function on a RT target to send an analogue signal to the AO0. And what happens is that I only get short pulses every time the DAQ function is active. The failure is not recognizable when working with a period of 1 ms, but when switching to slower rates it is clearly visible.

I'm using the following task options:  

Sample (On Demand)

Terminal Config: RSE

Min 0 V

Max 4 V

Do I have to use the DAQmx timing function or something like that?

When I use the standard RT VIs the RT wizard produces I can use only the DAQmx write function an it simply works.. tested it with a flat sequence structure with 4 frames, 2 for different output signals and 2 for waiting times. So I think its a programming failure.. 

I have no idea what my fault is, any suggestions?

Thanks

[PackersFan · Accepted solution]

You should definitely be using start task and clear task functions instead of a single write.  Take a look at some of the DAQmx examples in LV if you're not sure what I mean.

My guess is that since you are using a single write and not keeping the task alive, the task is being closed after the single point write.  When the task is closed, LV is automatically setting the output to zero.

[jLeschke]

Thanks for your quick reply!

I'm going to check that today and will post the results afterwards.

Bye, Jan

[jLeschke]

Problem solved, thank you again!

One Task appears multiple times in the main VI, so it wasn't clearly defined which operation is to execute.