Once an eye diagram measurement is begun and there is an eye diagram
displayed, different on-screen measurement tools may be used singly, or in
combination. Each measurement involves indicating with cursors and line
segments regions of the eye diagram that are of interest, and a parameter
or parameters associated with each measurement tool in use is reported in
a (usually) separate area of the display. An Eye Limits measurement allows
the specification of a point within an eye diagram, whereupon it finds and
reports the eye diagram coordinates first encountered along horizontal and
vertical lines extended from the selected point (i.e., "eye opening"
size). The coordinates of the point itself are also reported. A Four Point
Box measurement allows the construction on the eye diagram of a rectangle
having sides parallel to the coordinate axes of the eye diagram. The
coordinates of the rectangle are reported, as well as information about
the number of points on the eye diagram that occur on or within the
rectangle. A Six Point Box and a Diamond may be defined and used in a like
fashion. A Slope Tool uses two end points to define an intervening line
segment, whose slope and location can be adjusted to match some region of
interest on the eye diagram. The pertinent information about the line
segment and its end points is then reported. A Histogram measurement may
be performed on any selected slice of the eye diagram. The histogram is
thus of a distribution of number of hits versus either time axis location
at a fixed voltage, or voltage at a fixed time location. Duplicate cursors
appear on both the line defining the slice and within the histogram.
Either cursor can be grabbed and moved, which then also moves the other.
The scale for the number of hits for either histogram may be either linear
or logarithmic.
