Quantum Data 881 - Manual (Page 1189)

881/882 Video Test Generator User Guide (Rev A.22) 1073
• The box in the center track (marked “1X”) moves one scan line vertically and one pixel
horizontally for each vertical frame of refresh.
• The seven boxes to the right of the center track (marked “2X” through “8X”) move 2, 3,
4, 5, 6, 7, and 8 pixels and lines per frame, respectively.
• The seven boxes to the left of the center track (marked “/2” through “/8”) move one scan
line vertically and one pixel horizontally for every 2, 3, 4, 5, 6, 7, and 8 vertical frames
of refresh, respectively. These boxes are at the bottom of the tracks.
In cases where the next move would cause the box to move beyond the end of its track, it
immediately reverses and moves the correct distance in the opposite direction for the next
frame.
A continuously-running counter appears in the upper left corner of the image. The number
shown is the number of vertical frame refreshes that have occurred since the generator
was first powered up.
The secondary version draws a black image on a white background.
An example of the primary version of the Persist image is shown below:
Test Phosphor persistence
Purpose The phosphors on the face of most CRTs continue to glow for a short period of time after
the electron beam has stopped energizing them. This phenomenon is called persistence.
A certain amount of persistence is desirable in most applications. It prevents a flickering of
a displayed image that most users would find objectionable. On the other hand, a CRT
with an overly long persistence time causes moving objects to leave a blurred trail.
Method A flickering in the slower moving boxes indicates that the combination of refresh rate and
phosphor persistence is not suitable for long-term viewing.