A (Vertical Compress And Expand) - Tektronix 7D20 Operator's Manual

a
r
. a
~ .
`C "Y 1
lV . ~1" 1 V R ."8
V" i .= V " -t ". 8
Operating In st r uc tions - 7D2 0
waveform to its original display position . Waveform movement will automatically
stop at its original display position, at which time neither key will be illuminated . To
continue waveform movement past its original position, release the movement key
momentarily, then press and hold it again . The position of the cursor waveform GND
(plus or minus) with respect to center screen is shown in the VZR display (see Fig .
2-56) . Maximum movement in either direction is approximately 5 divisions (further
if expanded) . When the
'erence waveform is present (which means the cursor
waveform must be in HMAG or VS mode) these keys allow separation control
between the cursor waveform and its reference . These keys operate in this mode
even if the 7D20 is not in HOLD .
3857-158
Figure 2-56 . Cursor waveform with VZR (Vertical Zero Reference) altered by VPUP4 .
VCMPQ AND VXPDQ
(Vertical Compress and Expand)
With these keys you can vertically compress or expand the cursor waveform about
the center of the acquisition window . The cursor waveform can be expanded or
compressed, two increments (in a 1,2,5 sequence) from its original acquired vertical
scale factor .
When the cursor waveform is expanded or compressed, the respective VXPDQ or
VCMPQ key illuminates and the change in vertical scale factor will appear in the
display in the second from the bottom line labeled CSW . Because these keys have
opposing action, the opposite key is used to return the cursor waveform to its
original acquired vertical scale factor . At which time, neither key will be illuminated .
Waveforms being digitized cannot be vertically compressed or expanded and are not
affected by these keys except when HMAG or VS modes are selected and the
waveform is displayed . An attempt to do this results in the display of the warning
message "HOLD REOD" . Refer to prompts and warnings discussion given earlier in
this section . VXPDQ occurs about crt center whereas VCMPQ occurs about VZR
(Vertical Zero Reference) . This feature allows the user to position the expanded
waveform anywhere within the graticule area .
2- 109