## Solution

Your choice of sample rate depends upon the type of information you are interested in and the known attributes of your signal such as type and expected frequency.

To accurately measure the

**frequency **of a signal, you need a sample rate of at least twice the highest frequency component in the signal. This concept is known as Nyquist's theorem.

- The equation for frequency measurement is found below:

- where:

*f*_{max} is the maximum resolvable frequency

*f*_{Nyquist} is the Nyquist frequency

*f*_{s} is the sampling frequency

To analyze the

**shape **of the signal, you will need a sampling rate of at least ten times higher than the highest frequency component in the signal. In the equation above, you would divide by 10 instead of 2.

See

Using a Digitizer for Time-Domain Measurements for an illustrated discussion on this topic.

Once you have determined your sample rate, acquire at least one full period of the waveform. The number of samples that corresponds to can be shown through frequency resolution:

The frequency resolution (df) is dictated by the acquisition time:

where:

*T* is the period of the signal

*N* is the number of samples acquired

*f*_{s} is the sampling frequency

For example, a signal with frequency 50 Hz, there will need to be at least 0.02(1/50) seconds of data for a full period of the signal. At a sampling rate of 100 Hz for a frequency measurement, N will be 5000.