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Basic Applications- 2221 Operators
7. Adjust the TRIGGER LEVEL control for a stable
display.
More accurate phase measurements can be made by
using the X10 Magnifier to increase the sweep speed
without changing the SEC / DIV Variable control setting .
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Л
8. Set the SEC/ DIV switch to a sweep speed which
displays about one full cycle of the waveforms.
9. Position the displays and adjust the SEC/ DIV Vari
able control so that one reference - signal cycle occupies
exactly eight horizontal graticule divisions at the 50% rise
time points ( see Figure 6-9) . Each division of the graticule
now represents 45 ° of the cycle (360 °
8 divisions ) , and
the horizontal graticule calibration can be stated as 45 °
per division ,
EXAMPLE: If the sweep speed were increased 10 times
with the magnifier ( X10 Magnifier out) , the magnified
horizontal graticule calibration would be 45 ° /division
divided by 10 (or 4.5 ° / division ) . Figure 6-10 shows the
same signals illustrated in Figure 6-9 , but magnifying
the displays results in a horizontal difference of 6
divisions between the two signals .
Substituting the given values in the phase difference
formula :
Phase Difference
6 div x 4.5 ° /div = 27 °
10. Measure
the
horizontal
difference
between
corresponding points on the waveforms at a common hor
izontal graticule line (50% of rise time) and calculate the
phase difference using the following formula :
Phase
Difference
Horizontal
Difference x
(Divisions)
Horizontal
Graticule
Calibration ( deg / div )
TIME COMPARISON
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EXAMPLE: The horizontal difference is 0.6 division with
a graticule calibration of 45 ° per division as shown in
Figure 6-9.
In
a
similar
manner
to
" Amplitude
Comparison , "
repeated time comparisons between unknown signals and
a reference signal ( e.g. , on assembly -line test) may be
easily and accurately measured with the instrument. To
accomplish this , a reference signal of known time duration
is first set to an exact number of horizontal divisions by
adjusting the SEC/ DIV switch and the SEC/ DIV Variable
control. Unknown signals can then be compared with the
reference signal without disturbing the setting of the
SEC/ DIV Variable control. The procedure is as follows:
Substituting the given values into the phase difference
formula :
Phase Difference
0.6 div x 45 ° /div = 27 °
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1
CHANNEL 1
( REFERENCE)
CHANNEL 2
(LAGGING )
CHANNEL 1 ( REFERENCE )
CHANNEL 2
100
100
1 90
90
B
MEASURE
TIME FROM
ATO ( B
B
MEASURE
TIME FROM
A
А
ATOⓇ
JO
03 .
a
HORIZONTAL
DIFFERENCE
17
1 V
10us
д
П
п
П
П
П
OL Ime
8 DIVISIONS
( 360 ° )
HORIZONTAL
DIFFERENCE
4998-37
4998-43
Figuro 6-9 . Phase difference.
Figure 6-10. High -resolution phase difference .
6-11
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