General Operation
56 TVM Series Installation and Operation Handbook
Copyright © 2008, Harris Corporation
Eye Pattern Measurement Parameters/Considerations.
The display will show rise time, fall time, and amplitude. Rise and fall times are
displayed in ps for HD and ns for SD. Amplitude is displayed in mV.
The EYE measurement parameters are the most accurate with clean symmetrical data
signals. Cable type, length and horizontal jitter decrease the accuracy of the readings.
• Cable length: For best results use less than 2 meters of low loss cable such as
Belden 1694A.
• Jitter: When the horizontal jitter is 0.25 UI or more, the rise and fall readings
may display dashes instead of numbers. Amplitude will continue to be reported.
• Jitter high pass filters (HPF): The EYE measurements are calculated from the
displayed EYE on the screen. Changing the HPF filters allows the operator to
decrease the displayed jitter to less than 0.25 UI for EYE readings. Default
setting for the EYE HPF is 1000Hz.
If cursors are used to verify the measurements, the cursor readings may not match the
automatic parameter readings. The automatic EYE measurements use peak detectors,
histograms and curve fitting algorithms over time to give the most accurate readings.
Eye Pattern Parameters
The display will show rise time, fall time, and amplitude. Rise and fall times are
display in ps for HD and ns for SD. Amplitude is displayed in mV.
Jitter Meter and Eye Pattern Correlation
The jitter meter is intended to display the maximum value of jitter over time. The
correlation of values derived by using measurement cursors versus the jitter meter
could differ unless the eye pattern is displayed using the maximum persistence setting.
A normal persistence setting will make it more difficult to view pixels near the widest
sample points, which forces the placement of the measurement cursors to a lower
(narrower) jitter value.
Horizontal Magnification and Zoom in Eye Pattern Mode
Gain is used to set the range of amplification in the video signal. The standard gain in
the video signal is x1. The TVM Series can be used to set the gain amplification in the
video signal using the Gain group of buttons. The gain setting appears in the upper-left
portion of the waveform pane.
Press the MAG button to step through the available Horizontal Magnifications
of x1, x5, and x10: 1 ns, .20 ns, and .10 ns for SD or 250 ps, 50 ps, and 25 ps
for HD. The type of magnification along with the format displayed determines
how many “Eyes” are displayed. Table 3-19 describes the Horizontal Magnification
Conditions.
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