Data Acquisition Advice

[Otis]

Hi Laksh,

Are you able to run any of the DAQmx examples in CVI?
C:\Program Files\National Instruments\CVI80\samples\DAQmx

Try running just one of the really basic examples such as:
C:\Program Files\National Instruments\CVI80\samples\DAQmx\Analog In\Measure Voltage\Acq-Int Clk

If you run into similar issues then let us know so that we can see if this is more a problem on the CVI side of things or on the DAQmx side of things.

Regards,

[LAKSH]

Hello there

Many thanks for your reply.

I have resolved the winmain@16 problem by reinstalling the CVI application But, this time i have included the SDK option. I can perfectly run all your examples under DAQMX folder now.

>>I guess i have a real problem now. Iam trying to generate two simultaneous continuous analog signals, routed via two different physical analog output channels. I started from your example program ''ContGen-IntClk'' , created two analog physical channels, two seperate task handles, two seperate buffers...using malloc etc. I am getting run time errors because both the tasks trying to use the same function ''DAQmxWriteAnalogF64()'' and which ever task gets executed first, reserves that function resource and thus blocking the second task from accessing the function which results in run time error.

>>How do i plot two of these signals in the same graph plot?

Please advise if these is a better way of implementing DAQmxWriteAnalog? Does multithreading lead to the same problem of shared resourse?

Any help is much appreciated.

Many Thanks in advance.

[Hal_L]

Hi,

It sounds like you are trying to perform multiple analog output tasks at the same time. If these tasks are hardware timed, then you are limited to having a single analog output task running at one time with most devices. Here is the link to a knowledgebase with more information: Using Multiple Analog Output Tasks at the Same Time on the Same Board.

If your analog outputs have the same timing characteristics, then you will be able to output data on both channels within the same task. For example: to output data on one channel, you may specify your output channel as "Dev1/ao0." If you wanted to output data on channels 0 and 1, then you would use "Dev1/ao0:1." Remember, this solution is only valid if both analog outputs have the same characteristics. Otherwise, you will have to use the method mentioned in the knowledgebase. I hope that you find this information helpful.

Regards,

Hal L.