Scale Options
- Autoscale
Autoscale enables the vertical scale and range to be set automatically, which can make it easier to keep the live signal(s) visible in the plot. Sometimes, when a measurement doesn't appear as expected, setting Autoscale to Auto can solve the problem. When autoscale is off, the vertical scale of the plot can be manually adjusted by a two-finger pinch gesture within the axis label region of the plot. The range can be adjusted by a single-finger slide gesture within the axis label region. - Vertical Axis
Three vertical scale types are available for viewing spectra: Linear, Logarithmic, and dB. The desired scale type is determined by the selection of this control. -
Magnitude Scale
Tap on Magnitude Scale to select a vertical scale for the plot in standard units per division. Autoscale will be turned off. If the Vertical Axis option is set to dB, changing the Magnitude Scale will switch it to Lin. - dB Magnitude Scale
Tap on dB Magnitude Scale to select a vertical scale for the plot in dB per division. Autoscale will be turned off. If the Vertical Axis option is switched to Lin or Log, changing the dB Magnitude Scale will switch it to dB. - Level Type
This option selects the kind of magnitude (amplitude) level to be calculated and displayed for each frequency in the spectrum.
Level Type can be chosen independently for sound (signals with units of pascals) and signals with other units. The three options for amplitude are peak (pk), peak-to-peak (pp), and root-mean-square (rms). - Horizontal Axis
Two horizontal scale types are available for viewing spectra: Linear and Logarithmic. The desired scale type is determined by the selection of this control. - Frequency Units
This segmented control lets you choose whether to display frequencies in Hz or cpm (cycles per minute).
Display Options
- Apply Smoothing
This switch enables frequency data to be smoothed into fractional octave bands. Lower frequencies, below the point at which each fractional octave band includes at least one FFT frequency bin, are kept, but not smoothed. - Smooth Bandwidth
Use this segmented control to select the fractional octave bandwidth of the spectral smoothing. - Smoothing Type
Use this segmented control to select the type of spectral smoothing that will be applied.- Avg smoothing will simply compute the mean magnitude in each fractional octave frequency band.
- Max smoothing (selected by default) will pick the highest magnitude within each fractional octave frequency band.
- Min smoothing will pick the lowest magnitude within each fractional octave frequency band.
- In general, Max smoothing works better when peaks are present in the spectrum. Avg smoothing may be more suitable when making basic frequency response measurements using a broadband excitation signal.
Cursor Options
- Harmonic Cursors
Additional vertical cursors may be automatically placed at harmonics (integer multiples) of the current (fundamental) cursor frequency (enter a value up to 128). When more than zero harmonic cursors are active, the FFT Analyzer will display a THD (total harmonic distortion) value with the cursor data for each input channel. If a Uniform data window type is also selected, a THD+N (total harmonic distortion plus noise) value will be displayed as well. THD values will only be meaningful if the measurement is configured appropriately. For example, THD can be measured using a 1 kHz tone with the cursor placed at 1 kHz (fundamental frequency). Ideally, the tone should be generated by the same physical audio device that is receiving the input signal, for synchronized sampling of the data and precise positioning of the tone in the spectrum. - Horizontal Bar
When working with multiple channels in the FFT analyzer, this option lets you choose which channel the horizontal cursor bar will be associated with. - Peak Track
The cursor may be configured to automatically move to the frequency of the peak value within the current spectrum. This option allows the peak track function to be disabled, or to track the maximum or minimum peak within the spectrum. A triple tap or triple click within the spectrum plot will advance the peak track selection. - Peak Track Channel
When working with multiple channels in the FFT analyzer, this option lets you choose which channel the peak track function will apply to (the channel whose spectral peak will be tracked by the cursor).
Imported Data
- Trace Opacity
Use this slider control to adjust the opacity of static data traces (loaded from data files) in the plot. - Trace Thickness
This segmented control can be used to select the thickness of the static frequency data traces in the plot.