Acquiring and Displaying Waveforms
TDS 684A, TDS 744A, & TDS 784A User Manual 3–43
Using InstaVu Acquisition Mode (TDS 700A Models Only)The TDS 744A and TDS 784A Oscilloscopes can use InstaVu acquisition mode
to reduce the dead time between waveform updates that normally occur when
digitizing storage oscilloscopes (DSOs) acquire waveforms. InstaVu mode can
capture and display transient deviations, such as glitches or runt pulses, often
missed during longer dead times that accompany normal DSO display. This
subsection describes how to use InstaVu mode and how it differs from normal
acquisition mode.
Figure 3–26 illustrates how InstaVu acquisition mode differs from the normal
acquisition mode used by digital storage oscilloscopes. Note that normal mode
follows a “capture waveform–digitize waveform-update waveform memory–dis-
play waveform” cycle. Normal mode misses short term deviations occurring
during the long dead times. Typical waveform capture rates are 50 waveforms
per second.
InstaVu mode increases the waveform capture rate to up to 400,000 waveforms
per second, updating the waveform array many times between displays. This
very fast frame rate greatly increases the probability that runts, glitches, and
other short term changes will accumulate in waveform memory. The oscilloscope
then displays the waveform at the normal display rate using variable or infinite
persistence. You can control how long the waveform persists on screen by
selecting variable persistence and setting a decay constant.
To turn on InstaVu mode, do either of the two following steps:
1. Press the front-panel button InstaVu. (See Figure 3–27.)
2. Press DISPLAY ➞ Mode (main). Push Mode again to toggle to InstaVu
mode. (See Figure 3–27.)
To turn InstaVu off, press InstaVu. Alternatively, press DISPLAY ➞
Mode (main), and then press Mode again to toggle to Normal mode.