Calibration—492/492P Service Vol. 1 (SN B030000 & up)
Performance Check
Table 3-6
SPAN/DIV vs TIME MARKERS
FREQUENCY
SPAN/DIV
Time Mark Generator
Marker Output
20 MHz
50 ns
10 MHz
.1 μβ
5 MHz
.2 /iS
2 MHz
.5 /xs
1 MHz
1 ms
500 kHz
2 MS
200 kHz
5 ms
100 kHz
1 0 ms
50 kHz
2 0 μβ
20 kHz
50 ms
10 kHz
.1 ms
5 kHz
.2 ms (Option 03)
2 kHz
.5 ms (Option 03)
1 kHz
1 ms (Option 03)
500 Hz
2 ms (Option 03)
11. Check Time/Div Accuracy (accuracy within 5%
of time selected)
a. Test equipment setup is the same as that required for
step 1 0 .
b. Apply the Marker Output from the time mark gener
ator directly to the RF INPUT and the Trigger output to the
492/492P EXT TRIG connector on the back panel. Set the
controls as follows:
FREQUENCY «1 MHz
FREQ SPAN/DIV 100 kHz
RESOLUTION BANDWIDTH 10 kHz
REF LEVEL -2 0 dBm
TIME/DIV 50 ms
Triggering EXT
Min RF ATTEN 20 dB
c. Apply 50 ms time markers. Tune the FREQUENCY
toward 0 Hz as the FREQ SPAN/DIV is reduced to zero, so
time markers are displayed on the time domain display (see
Fig. 3-9). Adjust FREQUENCY if necessary.
d. Use the horizontal position control to align a marker
on the 1st graticule line; then check the displacement of
markers from their respective positions over the center eight
divisions. Individual marker displacement must not exceed
5% or 2 minor divisions.
m. Remove the time mark generator signal and
reconnect the comb generator to the RF INPUT. Modulate
the 500 MHz comb generator with 2 *ts (500 kHz) markers
by applying the Marker Output to the Pulse Input of the
comb generator. Change the REF LEVEL to -2 0 dBm and
tune the FREQUENCY toward 500 MHz until 500 kHz
markers are displayed over the center eight divisions of
display.
n. Check the 500 kHz/div span accuracy.
o. Reduce the RESOLUTION BANDWIDTH to 1 kHz,
then reduce the FREQ SPAN/DIV setting and time marks
(see Table 3-6) to check the accuracy for the 50 kHz
through 10 kHz FREQ SPAN/DIV selections.
p. For Option 03 instruments, reduce the RESOLUTION
BANDWIDTH to 100 Hz and set the TIME/DIV to 50 ms.
Check the 5 kHz through 500 Hz FREQ SPAN/DIV accura
cy. (This procedure will not yield the best amplitude display
but it will produce a readable frequency display.)
3odbh r s n
-t-i i i
.
1
..
Position marker on graticule line
50Κ£/
. , ^ « -ϊ fcJ « « a .
F1". 3-9. Display to illustrate how timing accuracy is checked.
3-22
REV AUG 1981
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