|NI-SCOPE (English | Japanese)|
Sample rate, specified in samples per second (S/s), is the rate at which a signal is sampled and digitized by an analog-to-digital converter (ADC). According to the Nyquist theorem, a sample rate at least twice the highest frequency of the signal produces accurate measurements if the analog bandwidth is wide enough to let the signal pass through without attenuation. A higher sample rate captures more waveform details for the time domain measurements. The following figure illustrates a 1 MHz sine wave sampled by a 2 MS/s ADC and a 20 MS/s ADC. The faster ADC digitizes 20 points per cycle of the input signal compared with 2 points per cycle with the slower ADC. In this example, the higher sample rate more accurately captures the waveform shape.