Tektronix 7B85 Instruction Manual page 91

Performance Check and Adjustment-7B85
d. Position the display for 1 marker/div over the center 8
divisions of intensified display.
e. Set the DELAY TIME control to start the first intensi-
fied zone on the time marker that is nearest the second
graticule line. Set the
~
TIME control to start the second
intensified zone on the time marker that is nearest the tenth
graticule line.
f. Further adjust the
~
TIME control to horizontally align
the time markers of the first and second delayed-sweep
traces.
g. CHECK-for a
~
TIME readout between 795.6 ns
and 804.4 ns.
NOTE
The limits in part g and Table 5-3 are derived from the
Performance Requirement in the Specification
section.
EXAMPLE: The Performance Requirement for L1
TIME accuracy at O. 1 I's/DIV is:
Within (0.5% measurement
+
0.03% full scale
+
1
least significant digit).
For an 8 division measurement (80 ns), the accuracy
is:
±(O.5% of 800 ns
+
0.03% of 1000 ns
+
0.1 ns)
=
±(4.0 ns
+
0.3 ns
+
0.1 ns)
=
± 4.4 ns
Therefore, the specified limits for a measurement in-
terval of 800 ns are:
800 ns ± 4.4 ns
=
795.6 ns to 804.4 ns.
h. CHECK-Follow the procedure outlined in parts c
through 9 and check for ~ TIME accuracy as given in Table
5-3.
B 15. Check .:l TIME Linearity
a. Set the TIME/DIV switch to 1 ms.
b. Set the time-mark generator for 0.5 ms markers and
set the companion time-base unit for a 10 f.Ls/div sweep
rate.
5-16
Table 5-3
~ TIME ACCURACY
Companion
7B85 Time Base Time ~
Time Readout
TIME/DIV Sweep Rate Markers
Range
.1
f.Ls
10 ns
.1
f.LS
795.6 ns to 804.4 ns
.2
f.LS
20 ns
.2 f.LS 1.591 f.LS to 1.609
f.LS
.5 f.LS 50 ns
.5 f.LS 3.977
f.LS
to 4.023
f.LS
1
f.LS
.1
f.LS
1
f.LS
7.956 f.LS to 8.044
f.LS
2
f.LS
.2
f.LS
2
f.LS
15.91 f.LS to 16.09
f.LS
5
f.LS
.5
f.LS
5 f.LS 39.77
f.LS
to 40.23
f.LS
10 f.LS 1
f.LS
10
f.LS
79.56 f.LS to 80.44 f.LS
20 f.LS
2
f.LS
20
f.LS
159.1
f.LS
to 160.9
f.LS
50
f.LS
5
f.LS
50
f.LS
397.7
f.LS
to 402.3
f.LS
.1 ms
10
f.LS
.1 ms
795.6
f.LS
to 804.4 f.LS
.2 ms
20
f.LS
.2 ms 1.591 ms to 1.609 ms
-
.5 ms
50
f.LS
.5 ms 3.977 ms to 4.023 ms
1 ms
.1 ms 1 ms 7.956 ms to 8.044 ms
2 ms .2 ms 2 ms
15.91 ms to 16.09 ms
5 ms .5 ms 5 ms
39.77 ms to 40.23 ms
10 ms 1 ms 10 ms 79.56 ms to 80.44 ms
20 ms
2 ms 20 ms 159.1 ms to 160.9 ms
50 ms 5ms 50 ms 397.4 ms to 402.6 ms
.1 s
10 ms .1 s 794.9 ms to 805.1 ms
.2 s 20 ms .2 s
1.589 s to 1.611 s
.5 s 50 ms .5 s
3.974 s to 4.026 s
c. Position the delaying- and delayed-sweep traces hori-
zontally to start on the first graticule line.
d. Set the DELAY TIME control to place the first intensi-
fied zone on the time marker that is between the first and
second graticule lines (second time marker).
e. Set the ~ TIME control to place the second intensified
zone to the time marker that is 0.5 division from the first
intensified time marker (third time marker).
f. Set the
~
TIME control to precisely align the delayed-
sweep traces.
REV AUG 1981