Tektronix CSA8000 Series, Service Manual

Page: 184 / 354

Electrical Sampling Modules
4–80
CSA8000 & TDS8000 Instruments and Sampling Modules
H
make sure the channel under test is selected in the Source menu.
H
choose Select Meas > Amplitude > Min.
H
select the Region tab.
H
set Gate G2 to 46%.
H
set Gates on (check).
h. The Max and Min measurements are now set to include the region of
250 ps to 20 ps before the edge. The aberration specification over this
region is
3%, which is 30 m
r
for a 1
r
step. Since the reference is
-1
r
, the Max and Min values should be within -1.030 to -0.970
r
to
meet the 3% specification.
i. Calculate and take down for later use the peak aberrations in percent
using the formulas (with Max and Min in m
r
units, not
r
):
H
positive aberration (%) = (1000+Max) * 0.1
H
negative aberration (%) = (1000+Min) * 0.1
For example: if Max = -989 m
r
and Min = -1.003
r
,
positive aberration (%) = (1000 + (-989)) * 0.1 = +1.1
negative aberration (%) = (1000 + (-1003)) * 0.1 = -0.3
NOTE . The aberration can have either a positive or negative sign. Both
aberrations could have the same sign when the waveform does not cross the
reference line in the region being checked.
j. In the Horz Setup dialog box:
H
set Horizontal Reference to 50%.
H
set Horizontal Scale to 2 ns/division.
k. In the Meas Setup dialog box for Meas2 (Region tab selected), set Gate
G2 to 49%.
l. Select Meas1, set Gate G2 to 49%.
m. The Max and Min measurements are now set to include the region of
10 ns to 200 ps before the edge. As before, the aberration specification
over this region is
3%, so the Max and Min values should be within
-1.030 to -0.970
r
.
n. Calculate the peak aberrations in percent using the formulas (with Max
and Min in m
r
units, not
r
):
H
positive aberration (%) = (1000+Max) * 0.1