# What is the minimum sampling duration to capture a given frequency?

Due to the Nyquist rate, you need to sample twice as fast as the highest frequency you want to measure. Then when you do a FFT the number of samples determines the number of bins and thus the frequency resolution.

But what about the lowest frequency you want to measure? I would think your sampling duration needs to be at least as long as one cycle of your lowest frequency.

Is this true, or can you register $20$ $Hz$ from a dozen samples at $44$ $kHz$?

If this is true, how long do you need to sample, and how do you limit the number of bins?

• Rule of thumb - one period of your wave. – jojek Mar 6 '15 at 12:36