Tektronix CSA8000B - Manual (Page 217)

Using Masks, Histograms, and Waveform Databases
CSA8000B & TDS8000B User Manual 3- 143
Mask Counts. The instrument lists statistics for each mask (polygon) in the
enabled standard (or user) in the Mask readout on the right side of the instrument
screen. Each mask is listed by its number, with its count of hits, the number of
hits common to all masks, and the total count of waveforms acquired.
Mask Editing. Masks can be edited, in which case they become a User mask.
Some tips on creating and using masks follow:
H When editing, locate one point along the left edge or right edge of the mask
further left or further right than any other point. You can still create straight
lines along the edge; just place one point further left of right than the others
on the edge.
H The vertices numbers increase according to their order from left to right. The
instrument reassigns numbers to vertices during mask creation or editing to
hold to this rule.
H When adding new points to a mask, the instrument determines their location
in the mask as follows (see Figure 3--26):
a. Defines an imaginary line between the left-most vertex and right-most
vertex in the mask.
b. Defines all points above the imaginary line as the top of the mask; all
points below as the bottom of the mask.
c. Inserts new user-added points above the imaginary line into the top of
the mask; inserts new user-added points below the imaginary line into
the bottom.
H To create a mask with a concave area, create several masks to cover the same
area. Data falling into two overlapping masks is counted only once as part of
the total mask hits.