DAQmx Timing (On Demand).vi

[AlexandreFSilva]

Hi!

I am doing a work that uses Cyclic Voltammetry technics. I am trying to use the example from this page "Measuring Cyclic Voltammetry for DAQmx" with a NI USB-6009 card and NI DAQmx drivers.

The problem is that, when I try to run the file appears this error:

Error -200077 occurred at Property Node DAQmx Timing (arg 1) in DAQmx Timing (Sample Clock).vi:2->cv_scan->cv.vi

Possible reason(s):

Requested value is not a supported value for this property.

Property: SampTimingType
You Have Requested: Sample Clock
You Can Select: On Demand

Task Name: _unnamedTask<2>

I know that the USB-6009 only support the On Demmand but the problem is that this type of timming is not present for choose! How can I find it? I think I miss the file "DAQmx Timing (On Demand).vi", or something like that!

Thank you for helping!

[Steve289]

Hello AlexandreFSilva,
    This is my first reply so bare with me.  I have used the USB-6009 and to aquire analog input  either create a global channel or task in MAX or create a Task or access a physical channel directly in Labview.  If you create a task for multi channel DAQ the timing should be set by defualt to ON Demand.  Once this is done just dropp a Task or Channel constant or control on your block diagram and an Ai Read function inside a loop.  The timing for the On Demand DAQ will be controlled by the WAIT value that you place inside the loop.  From what I get from your question it sounds like your creating everyting in Labview and using the Timing Function before you start your actual DAQ.  The Timing Function is not needed when using On Demand DAQ timing that is why it is not an option.  Block Diagram Flow listed below:
Global Channel created in MAX:
    Channel Constant or Control  -->  Loop  --> AI Read  --> after loop  --> Stop Task  --> Clear Task
Physical Channel Accessed in Labview:
    Physical Channel Constant or Control  --> Create Task/Channel  --> Start Task  --> Loop --> AI Read
             --> after loop  --> Stop Task --> Clear Task
The Stop and Clear Task are not needed for the Global Channel that you created in MAX and will not throw any errors if left out but is good code to implament.  The flow that I listed was pulled out of my head so forgive me if it is slightly off.  Simply stated though, you do not need to include the Task Timing Function in your code and if you remove it everything should work properly.  Don't forget a WAIT function in your loop, one sample will be read for every value of the WAIT statement.
Goodluck and I hope I did not make things any more complicated or confusing.

Steven.