seven
horizontal
divisions, can be determined
by
using the
time
duration
formula:
Time
Duration = 1.37 X 50 µs X 7 = 480 µs
This answer can be converted to
frequency
by taking
the reciprocal
of
the time
duration
(see applications on
Determining
Frequency). ·
PHASE DIFFERENCE
MEASUREMENTS
Use
either
the CHOP
or
ALT
mode. Set the A TRIGGER
SOURCE switch
to
CH
1.
The reference signal should
precede the comparison signal in time. Use coaxial cables
or
probes
that
have equal
time
delay
to
connect the signals
to
the
input
connectors.
If the signals are
of
opposite
polarity, set the INVERT
pushbutton
to invert the Channel 2
display
(signals may be
of
opposite
polarity due to 180° phase difference; if so,
take this into
account
in the final calculation). Set the CH 1
and CH 2 VOL
TS/DIV
switches and
the
CH 1 and CH 2
VAR
controls
so the displays are equal in amplitude.
Set the
TIME/DIV
switch
for
about
a one-cycle
waveform. Position the
display
and turn the A VAR
TIME/DIV
control
for
1 reference signal cycle in exactly
eight
divisions (see Fig. 23). Each
division
of
the graticule
CHANNELl
CHANNEL 2
(REFERENCE)
(LAGGING)
r
··I\···
··V
100
..
. .
.
...
..
. .
..
..
I
90
)/
,
V'"
.......
~
K
/
"\
'I\.
,@
V1
v
r\
\
\.
N
7
v
-
--0-~
'!\
~
I
iN
'\
/'i
I
I
i'\.
'\
/
v
I
: "
.....
"'-.......
~
HORIZONTAL 1
I
~
....
..
DIFFERENCE-~
·!--··
.
..
. . .
..
1.
8 DIVISIONS
0
(360)
Fig.
23.
Phase difference.
.
...
ii
J
v/
v
..
. .
MEASURE
TIME FROM
ATOB
1737·20
represents 45°
of
the cycle (360°
...;-
8 divisions =
45° /division). The sweep rate can be stated in terms
of
degrees
as
45° /division.
Measure the horizontal difference between
correspon-
ding
points on the waveforms and
multiply
the distance
measured (in divisions) by 45°
/division
(sweep rate) to
obtain the
amount
of
phase difference.
46
466/464 DM44 Operators
@
I
I
I
I
I
I
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