Displaying Frequency Information from Transforms
The discrete implementation of the Fourier transform maps a digital signal into its Fourier series coefficients, or harmonics. Unfortunately, neither a time nor a frequency stamp is directly associated with the FFT operation. Therefore, you must specify the sampling interval Δt.
Because an acquired array of samples represents a progression of equally spaced samples in time, you can determine the corresponding frequency in hertz. The following equation gives the sampling frequency fs for Δt.
| fs = 1/Δt | (A) |
The following block diagram belongs to a VI that properly displays frequency information given the sampling interval 1.000E – 3 and returns the value for the frequency interval Δf.
The following front panel shows the display and Δf that the VI with the previous block diagram returns.
Two other common ways of presenting frequency information are displaying the DC component in the center and displaying one-sided spectrums.