National Semiconductor ADC081500DEV, Instruction Manual

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12.0 Appendix C - Using WaveVision Plots
The WaveVision software provides several tools to help you interact with plots. A toolbar appears above
each plot, similar to Figure 4.
Figure 4: WaveVision Plot Tools
Seen from left to right, the following tools are available:
Plot Actions menu: This menu contains commands that pertain to this particular plot. You may export
the plot data to a file, print the plot, save it as a graphic, or change the plot’s colors.
Plot Options : This button opens a dialog box with options that pertain to this particular plot. You may turn
off labels, annotations, or other elements in this dialog. The WaveVision software maintains default
options for new plots. You may edit the default options by choosing
Default Plot Options
from the
Settings
menu.
FFT Options: The toolbar shown in Figure 4 is from an FFT plot, and thus contains a button to edit the
options for the FFT calculation. Depending upon the type of plot, various options may be present on the
toolbar. Please consult the appropriate section below for more information about these options.
Magnifying glass tool: This tool allows you to zoom in and out to see fine details in the plot. Click and
drag a box from upper-left to lower-right to zoom in on a particular region of your plot. Click and drag a
box from lower-right to upper-left to zoom out.
With the magnifying glass tool selected, click the right
mouse button to return to a normal, 100% view.
Arrow Tool:
The arrow tool is used to select, move, and edit annotations. To edit an annotation, double
click it with the arrow tool. To delete an annotation, select it with the arrow tool and press the
Delete
key
on your keyboard.
Line Annotation Tool:
To draw lines on the plot, select this tool. Drag to draw new lines. To add
arrowheads, or fix the endpoints of the line, double-click it with the arrow tool.
Text Annotation Tool: To draw labels on the plot, select this tool and click at the desired location in the
plot. To edit the justification, location, or text of an annotation, double-click it with the arrow tool.
The Waveform Plot
The Waveform plot shows you the raw samples collected from the hardware. This plot is mainly used to
verify the integrity of collected data – the waveform is the best view in which to diagnose a distorted signal,
an irregular clock, a low-amplitude signal, and many other common ADC system problems.
The Waveform plot also quickly shows you how much of the ADC’s dynamic range your signal occupies.
The FFT Plot
The WaveVision software automatically computes a Fast Fourier Transform (FFT) of the sample set, and
displays the results in an FFT plot. The FFT plot is, in many respects, the heart of the software. The FFT
shows you the frequency content of your input signal. It marks the fundamental frequency, and a
selectable number of harmonics. It also labels their order and frequencies. It shows the power in the
fundamental and harmonics. Try hovering your mouse cursor over a harmonic to get information about it.
The FFT can be used to diagnose common ADC problems such as input spectral impurity, clock phase
noise, and clock jitter. The FFT plot also shows several statistics on the quality and purity of the collected