Brochure

Application Note
www.tektronix.com/tbs1000b2
Background
A limit test function directs the oscilloscope to monitor a
source waveform against a predefined template. It outputs
a pass or fail result by automatically evaluating whether or
not the source waveform falls within the boundaries of the
template. If any part of the source waveform exceeds the
template boundaries, a limit test violation is noted.
Standard limit testing uses a “+/-“ band type of template
that is created from a single reference waveform, generally a
“golden” waveform. The user specifies horizontal and vertical
tolerances to create a band around the “golden” waveform,
defining the limit test template envelope (Figures 1a and 1b).
When an acquired waveform is compared with the template,
each acquired sample point value is compared to the vertical
and horizontal min/max values of the template. Any source
waveform data point that falls outside the corresponding
template envelope is a violation.
In standard limit testing, the tolerance band is the same
height and width for the whole record, since it uses one single
reference line and the same vertical and horizontal tolerance
throughout the record. The advantage of the new area-based
limit testing is that the tolerance band can be almost any
shape, since it is based on two reference lines, although the
vertical and horizontal tolerance is still applied across the
whole record (Figures 2a, 2b and 2c).
Vertical
Tolerance
Vertical
Tolerance
Vertical
Tolerance
Horizontal
Tolerance
Vertical
Tolerance
Vertical Tolerance
Horizontal Tolerance
Horizontal
Tolerance
Horizontal
Tolerance
H
V
H
H
V
V
H
V
Horizontal
Tolerance
V
H
V
H
H
V
V
H
H
V
H
H
V
V
Vertical
Tolerance
Vertical
Tolerance
Vertical
Tolerance
Horizontal
Tolerance
Vertical
Tolerance
Vertical Tolerance
Horizontal Tolerance
Horizontal
Tolerance
Horizontal
Tolerance
H
V
H
H
V
V
H
V
Horizontal
Tolerance
V
H
V
H
H
V
V
H
H
V
H
H
V
V
Vertical
Tolerance
Vertical
Tolerance
Vertical
Tolerance
Horizontal
Tolerance
Vertical
Tolerance
Vertical Tolerance
Horizontal Tolerance
Horizontal
Tolerance
Horizontal
Tolerance
H
V
H
H
V
V
H
V
Horizontal
Tolerance
V
H
V
H
H
V
V
H
H
V
H
H
V
V
Vertical
Tolerance
Vertical
Tolerance
Vertical
Tolerance
Horizontal
Tolerance
Vertical
Tolerance
Vertical Tolerance
Horizontal Tolerance
Horizontal
Tolerance
Horizontal
Tolerance
H
V
H
H
V
V
H
V
Horizontal
Tolerance
V
H
V
H
H
V
V
H
H
V
H
H
V
V
Vertical
Tolerance
Vertical
Tolerance
Vertical
Tolerance
Horizontal
Tolerance
Vertical
Tolerance
Vertical Tolerance
Horizontal Tolerance
Horizontal
Tolerance
Horizontal
Tolerance
H
V
H
H
V
V
H
V
Horizontal
Tolerance
V
H
V
H
H
V
V
H
H
V
H
H
V
V
Figures 1a. and 1b. Conventional limit testing.
Figures 2a. 2b. and 2c. Area-based limit testing.