Acquisition time NI 6008

[anouardz]

Hello; I have a problem with time data acquisition in a single analog input using a potentiometer. The maximum duration that I could reach is 1 minute and 58 seconds with a sampling frequency of 1 kHz, and an observation of the graph in Labview and recording on excel. And this time decreases when using multiple analog inputs simultaneously. The error message that appears just after stopping the system is :

[crossrulz]

Looks like you got cut off in your posting.

It sounds like you are not reading the data enough.  You need to continuously use the DAQmx Read to keep the buffer clean and process the data as it comes in.  If you need all data points in the graph, then you need to use Append Waveform or Build Array to keep all of the values in a shift register.

If you can share your code, that would help us figure out where you are falling short.

[anouardz]

thank you for answer,

code with the excel file :

[crossrulz]

The problem with file IO is that it can get really slow.  Personally, I would just use the logging capability in the DAQ Assistant to stream the data to a TDMS file.  This bypasses a lot that your Write To Measurment File must go through.  So all you need to do is configure that logging capability, read the data, and put it into the chart.  No need for the Write To Measurement File.

On a side note, there is an input the the DAQ Assistant called Stop (F).  You should wire your stop button to that and use the Stopped output of the DAQ Assistant to the loop terminator.  This will allow the DAQ Assistant to do some clean up before your program stops.

[AgentAstronaut]

Check out this:

http://digital.ni.com/public.nsf/allkb/3E3D74E26B8A5B83862575CA0053E4B5

And this:

http://www.ni.com/white-paper/9574/en/