User guide

Parameters Tab
Note that if you modify the parameters on this page, you have to rerun the
measurement to update the results.
Set the criteria for moving to the next sample point:
• Number of Compared Bits
After this number of compared bits, the measurement stops for the current
sample point and moves to the next one.
The default is 1 million bits. That means, you can measure a bit error rate down
to 10
-6
(one error per million).
A smaller number reduces the duration of the whole Fast Eye Mask
measurement. A larger number increases the precision of the measured bit
error rates.
• Number of Errors
After this number of errors, the measurement stops for the current sample point
and moves to the next one. This allows you to speed up the measurement. You
can switch off this option if only the number of compared bits is important.
N O T E
The measurement moves to the next sample point when the first of the two criteria
is reached.
Set the criteria how the sampling points of the eye are displayed:
• Timing Unit
Choose between Unit Interval and Seconds to set the timing values for the
measurement points on the Parameters tab. This setting does not affect the
display of results.
• Threshold Type
Choose between Absolute, Offset,or Percentage to set the thresholds for the
measurement points:
– Absolute
You specify the thresholds for the measurement points as absolute
voltages.
– Offset
You specify the thresholds for the measurement points relative to the
threshold voltage of the actual sampling point.
– Percentage
You specify the thresholds for the measurement points as a percentage of
the current eye opening voltage of the error detector.
6 Advanced Analysis
312 Agilent J-BERT N4903B High-Performance Serial BERT