sampling freq parameter in butterworth filter

[barak]

Hello,
when i'm using butterworth filter as lowpass filter,
if i have a signal that is 20 hz and the noise is in 100hz.
if givig 20 in the low cut off parameter, what is the parameter i have to give to sampling freq?

thanks.

[Dennis_Knutson]

The sampling frequency is the acquisition rate of the daq device used to acquire the signal. For example, if you used AI Acquire Waveform with the default setting of 1000 samples/sec as the sample rate, your sampling frequency is 1000 hz.

[neophyte_ab]

I have a related question regarding the sampling frequency parameter.

I am using a NI 6363 on a PXIe-RT 1082 chassis to get some analog data from pressure sensors. For my application, I estimate that any frequency above 1 Hz is noise, and would like to get rid of it using a Butterworth filter.

My AI task acquires data at 1 kHz, and my DAQmx Read task is set to run every 100 ms, so I can expect about 100 data points every time the read VI executes. My question is, what do I do with these 100 data points? Or in other words, when I feed this array of 100 values into the Butterworth filter, what should I set the sampling frequency input as?

Would be great if someone could help me with this.

Thanks