Eye Width

The Eye mode Eye Width is a measure of the horizontal opening of an eye diagram. Two coordinate annotation labels are placed at the eye crossings. One label is placed at the left side crossing and the other label at the right eye crossing. Ideally, the eye width would be measured between the crossing points of the eye. However, jitter may appear on the waveform and influence the eye opening. To compute eye width, the crossing points of the eye are first located. Then a vertically thin measurement window is placed horizontally through the crossing points. The data within this measurement window is analyzed. This measurement window is created to be extremely small so that the width of the crossing points is not affected by the rise time and fall time of the waveform.

The eye width is determined by measuring the noise through the histograms as 3σ (standard deviation) from both the crossing points into the eye opening.

You can also choose to view eye width as a ratio of the time difference between the 3 σ points of the crossing point histograms relative to the time between adjacent crossing points (bit period).

If time format is selected, the measurement is listed in the table as Eye Width[Time]. If ratio format is selected, the measurement is listed in the table as Eye Width[Ratio].

Configurable Measurement Parameters

This measurement is affected by the following setting (click Measure > Configure Base Measurements):

• Eye Boundary tab

To measure

1. Select Eye/Mask Mode.
2. Click the toolbar's Eye Meas tab.
3. Click Auto Scale in the menu bar.
4. Click the More buttons to locate the Eye Width button.
5. Click the button and select the measurement format: Time or Ratio.

SCPI Command

:MEASure:EYE:EWIDth