Tektronix SPECMON3 Manual page 71

General Signal Viewing
of the colors are concentrated at either the low or high end of the density scale, so you can visually
discriminate finer differences between density values in that range.
Persistence Adjustments
Dot Persistence can be enabled for the "Bitmap" trace using the Settings control panel. The Persistence
can be displayed as Infinite or Variable. For Variable Persistence, you can select the time constant for
fading in seconds as shown in Figure 27.
Figure 27. The trace settings control panel allows user control of persistence parameters.
Figure 28 demonstrates the observed behavior of variable persistence when a CW signal, represented in
the first frame, is turned off. Even if the event was instantaneous and was confined within a single frame,
you will observe the color changing to indicate lower and lower density values, until the signal finally
disappears entirely.
Figure 28. With variable persistence, a brief CW signal captured by DPX remains in the display for an adjustable
period of time before fading away.
DPX Density Trigger
The standard DPX display shows you a clear picture of transients and other hard-to-find signals. The
version of DPX in instruments with option 200 goes well beyond helping you discover these difficult
to find signals by actually triggering on their appearance to capture them into acquisition memory for
in-depth analysis. If you can see it in the DPX bitmap, you can trigger on it.
Other trigger methods can detect signals that exceed an amplitude threshold, or even a sophisticated
amplitude-vs-frequency mask, but they can't find a signal at a particular frequency if another signal of
higher amplitude is sometimes present at that same frequency. The Runt trigger addresses some of these
signal-under-signal cases, but not all. As shown in Figure 29, the DPX Density trigger can discriminate
signals within a precise amplitude-frequency range without the operator having to know any characteristics
of the target signal besides where it might show up in the DPX Spectrum graph.
SPECMON3 & SPECMON6 Printable Help
DPX Primer
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