Delayed Sweep Delta Time Accuracy - Tektronix 2445A Service Manual

I.
Set:
Delta
TRACK/INDEP
HORIZONTAL
A SEC/DIV
B SEC/DIV
X10 MAG
TRACK
100 ns
1 0 ns (knob out)
On
m. Select 0.1-µs time markers from the Time-Mark
Generator.
n. Adjust the
~
and
~
REF OR DL Y POS controls for a
~t readout display of 800.0 ns.
o. Adjust the Horizontal POSITION control to align the
leading edge of the 2nd time marker on the A sweep with
the 2nd vertical graticule line.
p. Rotate the TRACE SEP control CCW to separate
the traces.
q. Adjust the
~
REF OR DL Y POS control to intensify
the 2nd and 10th time markers (of the A sweep) and
display the leading edges of the displayed B-sweep time
markers in the center area of the graticule.
r. VERIFY-The horizontal distance between the lead-
ing edges of the B-sweep time markers is within the con-
servative guideline listed in Table 4-10. If this guideline is
met, accuracy between each marker is ensured, and the
following CHECK step need not be performed.
NOTE
To easily maintain the A SWP and B SWP difference
while testing Delta Time, use the following method:
1 . Starting with the 1-µs test in Table 4-10 (X 10
MAG Off), turn TRACKING off.
2. Press and hold the TRACKING button, then
push the SEC/DIV knob in. This will lock the
sweeps together at that difference.
3. Pull the SEC/DIV knob out.
The fastest sweep speed at which the X100 difference
is maintained is with an A SEC/DIV of 1
µs
and a B
SEC/DIV of 10 ns, after which only the A-sweep speed will
change with the SEC/DIV knob. Push TRACKING to
unlock this setup.
Performance Check-2445A/2455A Service
s. CHECK-The horizontal distance between the lead-
ing edges of the B-sweep time markers is within the
specified limits given in Table 4-10. The limit given is for
separation between the 2nd and 10th marker; however,
separation between the 2nd marker and each succeeding
marker should also be checked, calculating the limits from
the specification as listed at the top of the table.
t. Repeat part r (and s if necessary) for each combina-
tion of A SEC/DIV, B SEC/DIV, and X10 MAG settings
listed in Table 4-10. The
~t
readout should be set to indi-
cate eight times the A SEC/DIV setting. At the slowest
sweep speeds, the B SEC/DIV knob can be pushed in (in
B Sweep only) to increase the display repetition rate.
Table 4-10
Delayed Sweep Delta Time Accuracy
Displayed Separation of
Delayed Time Markers
(for 2nd and 10th markers)
Specified
Limit:
(0.3% time)
interval
A SEC/DIV B SEC/DIV Conservative +0.1% of
and Time as Displayed Guideline full scale-
Markers on Readout (divisions) divisions
0.1
µS
1 ns
8
2.4 3.4
0.2
µS
2 ns 8 2.4 3.4
0.5
µS
5 ns 8 2.4 3.4
1
µS
10 nsb
2.4 3.4
2
µS
20 ns 2.4 3.4
5 µS 50 ns 2.4 3.4
10
µS
100 ns 2.4 3.4
20
µS
200 ns 2.4 3.4
50
µS
500 ns 2.4 3.4
0.1 ms 1
µS
2.4 3.4
0.2 ms 2
µS
2.4 3.4
0.5 ms 5
µS
2.4 3.4
1 ms 10
µS
2.4 3.4
2 ms 20
µS
2.4 3.4
5 ms 50
µS
2.4 3.4
10 ms 100
µS
2.4 3.4
20 ms
200
µS
2.4
3.4
50 ms 500
µS
2.4 3.4
0.1 s 1 ms 2.4 3.4
0.2 s 2 ms 6.4 7.4
0.5 s 5 ms 6.4 7.4
•x10 MAG On.
bFor remainder of table, turn X10 MAG Off.
4-27