buffering and number of sample

[heang]

hello

i was using ni daqmx to acquire analog signal. the sample number i put is 2000 then the sample to read is 2000,the result is fine. if i do not put the sample to read to any valid value, it is set to -1. here my question goes, what if i put the sample to read is 1000 while maintaining the sample number(2000), how likely this changes affects my result?does it mean it takes 2 second to retrieve the data from the buffer?
as what i know is that the sample to read is the portion from the buffer size. am i allowed to put the sample number equal to sample to read?does it mean it takes 1 second to read from the buffer ?.
here another question goes. changing the sample number and sample to read will not affect the accuracy of the acquisition?the accuracy is just depending on the sampling rate, can i assume this?



thanks
regards

[devchander]

what if i put the sample to read is 1000 while maintaining the sample number(2000), how likely this changes affects my result?does it mean it takes 2 second to retrieve the data from the buffer?

In this case, if you are using a Normal while loop, your DAQmx read will execute 2 loops in one second and retrive from the AI buffer :1000+1000= 2000 samples in one second

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am i allowed to put the sample number equal to sample to read?does it mean it takes 1 second to read from the buffer ?.

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Yes you can put number of samples to read ( specified in DAQmx read function) = Sampling rate ( specified in the DAQmx Timing function)

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changing the sample number and sample to read will not affect the accuracy of the acquisition?the accuracy is just depending on the sampling rate, can i assume this?

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Yes you can assume this. But your Sampling rate must satisfy the Nyquist criterion for the signal that you are acquiring