Tektronix 7B10 Instruction Manual page 21

Operating lnstructions-~7B1
0
Fig,
2-5.
Measuring
the period
and
determining
the
frequency
of a
displayed
waveform.
5.
Set the
vertical
deflection factor
and
position control
for
about a 5-division display, vertically
centered on
the
graticule.
6
Set the
TIME/DIV
switch
and POSITION
controls
for
a
complete
cycle
displayed within the center
8
graticule
divisions
as
shown
in
Figure 2-5.
7.
Measure
the horizontal distance
in
divisions
over
1
complete cycle
of
the displayed
waveform.
Using
the formula:
Frequency
=
1
period
Substituting values:
Frequency
=
=
1.43 kilohertz
0.7
ms
RISE-TIME
AND
FALL-TIME
MEASUREMENTS
Perform the following procedure
to
measure
the
rise
time
and
fall
time
of a
displayed waveform:
1
Install
the time base
unit
in
a
mainframe
horizontal
compartment
(either
A
or
B
horizontal
in
a four-
compartment
mainframe).
2 Connect
the signal to
be
measured
to
the
vertical unit
input.
3.
Set the
mainframe
horizontal-
and
vertical-mode
switches
to
display the
time base and
the
vertical unit
(Check
that
the time
base
VARIABLE
(CAL
IN)
control
is
pushed
in
and
the
HOLD
OFF
control
is
in
the
MIN
position
)
4.
Set the
TRIGGERING
switches and
LEVEL
control
for
a
stable display (see
General Operating Information
for
selecting
proper
triggering).
5.
Set the
vertical
deflection factor
and
position controls
for
a vertically-centered
display with
an
exact
number
of
divisions of
amplitude.
8.
Multiply the horizontal distance
measured
in
Step 7 by
the
TIME/DIV
switch
setting.
(Divide the
answer
by
10
if
sweep
magnification
is
used.)
Example:
Assume
that the horizontal distance
over
1
complete
cycle
is
7 divisions,
and
the
TIME/DIV
switch
setting
is .1
ms
(see
Fig. 2-5).
Using
the formula:
Horizontal
TIME/DIV
Period =
_cljslan^e_
Magnification
Substituting values:
Period
"
- 0.7
millisecond
1
9.
Determine
the frequency
of
the displayed
waveform
obtained
in
steps
1
through
8 by taking the reciprocal of the
period
of
1
cycle.
Example:
Assume
that the period
of
the
displayed
waveform
is
0.7 millisecond.
6.
Set the
TIME/DIV
switch
and
POSITION
control
to
display the rising or falling
portion
of
the
waveform
within the center 8 graticule divisions as
shown
in
Figure
2-6
(see
General Operating Information
in
this
section
for
discussion of timing
measurement
accuracy)
7 Determine
rise
time
or
fall
time by
measuring
the
horizontal
distance
in
divisions
between
the point on
the
rising or falling portion of
the
waveform
that
is
10%
and
the point
that
is
90%
of
the
total
display
amplitude
(see
Fig 2-6).
NOTE
The
left
edge
of
the oscilloscope graticule
is
scribed with
0.
10,
90.
and
100%
lines
for
convenience
when
measuring
rise
time or
fall
time
To
use
this feature,
adjust the
vertical
deflection factor
and
position controls
to
fit
the display
between
the
0 and 100%
graticule
lines.
Then
measure
the horizontal distance
between
the points
where
the
waveform
crosses the
10% and
90%
graticule
lines.
8 Multiply the horizontal distance
measured
in
step
7
by
the
TIME/DIV
switch
setting. (Divide
the
answer
by 10
if
sweep
magnification
is
used.)
(CD
2-9