SLWU087E november 2013 – june 2023
The Single Tone FFT screen is shown in Figure 3-29. The larger central pane displays the FFT power spectrum, whereas the calculated statistics are grouped into categories on the left side of the screen. Settings and inputs relevant to the test are entered in drop-down menus or text input boxes on the bottom left portion of the window. .
The red horizontal line shown is the RMS line. This line indicates the RMS average of the noise floor of the FFT plot. The RMS average is computed over all of the FFT bins except the bin containing the input frequency. More precisely, the RMS line = SINAD + FFT Record Length Process Gain where FFT Record Process Gain = 10log(number of points/2).