sampling rate issue with DAQmx function in PCIe 6363 card

[GopalSarkar]

Hi Friends

I am new in NI data acquisition card( PCIe 6363). Presently I am using visual studio tool trough NI-DAQmx C function for all real data process.

Now, i am testing with one analog input signal channel  and one analog output signal channel. But in my observation in realtime , when i have configure

my sample rate is above of 200Khz , output signals are large shifted  & not shown same frequency in output channel what i have inserted in my input channel.

but within 200KHz sample rate, there have no issue  for any input analog signal process. I want to set sample rate is 1MHz & have to insert analog input data 100KHz amd My NI card max sample rate is 2MHz. So, i can't understand this problem, why this not work .

If, any one know the solution regarding my issue, kindly help me & give proper guidence.

Note: I have attached my sample C code for your reference.

Wait for your kind response.

Regards

Gopal

[GopalSarkar]

Need support ..

[Mathieu_R.]

Hello,

You are running a continuous acquisition. This means you delegate to the DAQ board the clocking of your acquisition, and gathering data to the RAM. This also mean you are responsible of reading the acquired data before the DAQ board entierly fills the buffer in RAM. At 200kS/s, if you are reading 10 samples per channels at a time, your program will have to do 20000 reads per second - loop time : 50µs. On a Windows plateorm, I think it cannot work properly. What is the CPU load when the program is running?

The same problematic applies to the generation: you are responsible of providing enought samples to the DAQ board in a given time, in order that the DAQ board can update its outputs at the desired sample rate.

Could you provide a screenshot of what is generated/acquired?

Try to increase the number of samples you read/write when calling DAQmxReadAnalogF64 and DAQmxWriteAnalogF64. I usually try to get a loop time greater than 10ms. 10ms @ 200kS/s means 2000 samples per read/write operation.

Best regards,

[GopalSarkar]

I have tested with your instructions.

have given input analog signal 20KHz with sampling frequency 1MHz..

Out put signal , i have got 5KHz approx.

I have attached my osciloscope snapshot which i have got during test.

wait for your next suggestion.