Units of Number of Samples and Rate Units for DAQ Assistant

[Tupaj]

Hi,

I am using the DAQ assistant to input an analog voltage from a NI data acquisition board. What is the difference between the number of samples and the rate in the DAQ assistant and what are the units of both?

Thanks.

[AnalogKid2DigitalMan · Accepted solution]

The number of samples is how many discrete measurements to make. The rate (per second) refers how fast to acquire the specified number of samples.

If number of samples is 100 and the rate is 1000 samples/second, then the acquisition would take 0.1 seconds (100 / 1000).

-AK2DM

[Vikingyong90]

Hi,

May I know the difference between the 2 following cases:

Case 1 : sample to read = 5000, rate =5000, then the acquisition is 1 second

Case 2 : sample to read = 100, rate = 100, then the acquisition is 1 second

Thank you

[Dennis_Knutson]

It's really basic. With a rate of 5000 samples/sec, you have one sample every .2ms (1/5000). At a rate of 100, you have one sample every 10 ms. The rate you use will depend on the frequency of the signal you wish to sample. If you are not familiar with Nyquist sampling theory, now would be an excellent time to do a little basic research before doing a data acquisition task.

[Vikingyong90]

Thanks for the reply.

But is the acquisition the same? 

I try to measure voltage waveform and display on chart.

Is this means that there be value output every one second?

Hope for guidance. Thank you.

[Dennis_Knutson]

There would be either 5000 or 100 values output every second - that is why the rate of called ' samples per second'.