Spectrum Plot Options
The spectrum display options dialog box can be activated by selecting the <Options><Plot Options><Spectrum> menu or by clicking on the options dialog icon button in the plot toolbar.
Plot Type: You can change between line and bar graphs by clicking on the toolbar controls or from the spectrum display options dialog box. For optimum display performance, the line or stepped bar graph option is recommended when using large FFT sizes and narrowband scaling. The bar graph option is recommended when Octave scaling is selected or when zoomed in with narrowband scaling.
Plot Top/Range/Bottom: The Plot Top and Range values determine the amplitude axis scale values. Plot Top is the value at the upper edge of the plot. The lower edge of the plot is always equal to the Top value minus the Range value. When Linear scaling is selected for the amplitude axis, the Plot Range value is set to zero and cannot be changed. When Log Magnitude scaling is selected for the amplitude axis, the Plot Range value changes to become the Plot Bottom value.
Peak Hold: Displays a secondary trace showing the highest amplitude values for each frequency bin. Selecting Fast, Medium or Slow will cause the peak hold values to temporarily hold before resetting. Forever will hold the values without releasing them. Stopping and restarting the processor will reset the peak hold values.
Pull Cursor to Trace: If this option is enabled, the measurement cursor will automatically "pull" to the spectrum trace along the amplitude axis.
Colors: The color of each plot feature can be changed. The "Default" button will restore the initial colors settings.
Grid Lines: Show or hide the grid lines.
Show Toolbar: Show or hide the plot toolbar. A small + or - button below the toolbar also controls this feature.
Show Overlay Controls: Show or hide the overlay controls on the right side of the Spectrum Plot. A small + or - button below the overlay controls also controls this feature.
Frequency Span: Although the displayed frequency span can easily be selected using the zoom buttons on the toolbar, you can also manually enter the span yourself. The span is limited to the total available span. The actual span displayed may vary slightly from the requested values because the values are adjusted to the nearest bin.
Display Update Interval: Controls how often the display is updated. This is useful on some laptop computers with slow display refresh rates to reduce flicker.
Show Total Power Meter: the total power meter is located along the right side of the spectrum plot and shows the "Total" power of the spectral data. This value is equal to the Total Power utility. A different weighting curve can be applied to this value (this is set in the Scaling dialog box). A small + or - button below the meter also controls this feature.
Show Zoomed Power Level: If enabled, the RMS Power level will be computed and displayed above the top left corner of the plot. This power level is computed for the currently displayed span and will change as you zoom in and out. Use this feature to compute the power within any segment of the spectrum. The weighting used for this calculation is the same as the spectrum weighting parameter in the scaling dialog box.
Copy these settings to all channels: This will copy the current Spectrum Plot option values to all other channels.
See Also: Spectrum Plot, Plot Toolbar