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.
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.
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).
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.
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).