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modem to report measurement
r
esults or control a signal router.
A relative to reference mode
allows normalizing to a signal
source or eliminate signal path
errors from the desired
measurement. Up to 2 video
references can be stored in
NVRAM. Additionally, after
downloading to a PC through the
V
M700T FTP driver, the video
reference can be uploaded to
another VM700T for reuse. A
running averaging mode can be
used to reduce the effect of noise.
When additional measurement
data is required a user can custom
configure measurement parameters
and report format.
A powerful Test Signal search
capability quickly and automati-
cally locates and identifies valid
test signals required for a selected
measurement, eliminating the
annoying and time consuming
task of manually locating
test signals.
Digital waveform monitor/
vectorscope
The VM700T Waveform mode
application provides real time
graphics displays of the video
signal allowing many additional
measurements to be made manu-
ally. Easy to use measurement
cursors are available to measure
time, frequency and amplitude
parameters of a video signal.
These cursors allow a very quick
and precise location of the 10%,
50% and 90% points on any
transition. Cursor mode also
employs an automatic calcula-
tion in the wave shape in the
center of the display
. The para-
meters calculated are sine peak-
to-peak amplitude, frequency,
and of
fset from blanking level.
This is very useful for frequency
r
esponse measur
ements with the
Multiburst signal.
The wavefor
m display can be
expanded around any point both
vertically and horizontally. Since
the data is digitized, the display
remains bright and easy to ready
at all expansion factors. The
scales automatically expand with
the waveform, so all units are
correct as displayed. A channel
dif
fer
ence mode (A-B, A-C, B-A,
B-C, C-A, and C-B) is also provided.
A
screen memory selection
enables Envelope mode, which is
useful for looking at teletext,
Jitter, or other changes over time.
Vector mode provides the normal
vectorscope display. The vectors
may be rotated or expanded, with
t
he rotation angle and gain values
displayed numerically on the screen.
A unique “Find ColorBars” feature
searches all video for ColorBars
and displays the vectors if found.
The vectors can be referenced to
either the selected channel’s burst
or the burst of one of the other
two channels or continuous
subcarrier. The phase difference
between the selected channel and
the reference is always displayed.
Select Line in both Waveform
and Vector modes can be used
to quickly specify any line for
display or automatic measurement
if it is the proper signal.
Picture mode
The signal source can be quickly
verified using the picture display.
Additionally, a “bright-up” line
select mode allows a user to
select any video line for use in
Measure mode or for viewing in
Waveform or Vector mode.
User programmable functions
Function mode is an extremely
powerful feature that allows a
user to store a sequence of user
operations as a macro function
for later “playback.”
For example, a set of measur
e-
ments (complete with hardcopy
commands) to be made on a
transmitter demodulator video
output, could be stored as a
function labeled “DEMOD.” The
function “playback” could then
be initiated manually, remotely
or completely automatically as a
user specified timed event.
Function files can be stored as a
text file on a PC for editing,
copying or uploading to another
VM700T. Other function capabil-
ities include controlling of external
serial devices such as video/audio
routers, switchers, signal generators,
telephone modems and many
other devices which support
RS232 communications.
Hardcopy
All information on the screen
m
ay be printed in high resolution
graphics on printers supporting
PostScript
®
, Hewlett-Packard
®
LaserJet™, DeskJet™, and
ThinkJet™, or 24-pin Epson
®
g
raphics via the Centronics
compatible parallel port or
standard RS-232C interface.
Automatic measurement results
in text format can be printed on
most ASCII printers using the
parallel or serial ports.
Remote Operation
The VM700T has a powerful and
fully documented remote control
language. The VM700T can
thus be operated from a remote
terminal via RS-232C to monitor
unattended transmission systems.
In addition, all files can be
uploaded to a main computer,
and downloaded to other
VM700Ts. Two different
protocols are supported: FTP
(File Transfer Protocol) and
TELNET. The user can also select
a “no protocol” mode of the
RS-232C interface when dealing
with low baud rates. However,
file transfers can only take place
with FTP.
Specifications
The performance requirements
cited in this section are valid
only within the following
environmental limits:
Temperature range of 0 to 50
degrees Celsius, with a
minimum warm-up time of 20
minutes. The following tables list
each measurement and its
performance requirement.
The range specifies the extremes
between which a measurement
can be made.
All measurement accuracies
specified are valid only with
nominal input signals of 1 volt
pk-pk (± 6 dB) with an unweighted
signal-to-noise ratio of at least
60 dB on the incoming signal and
a termination accuracy of ± 0.025%
(Tektronix PN 011-0102-01
or equivalent).
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