Table of Contents
Advertisement
1 1 . FREQUENCY MEASUREMENTS
Frequency measurements are made by measuring the
period of one cycle of waveform and taking the reciprocal
of this time value as the frequency.
Procedure:
1. Following the proceudre described in section 5 "Time
Measurements", measure the time of each cycle. The
figure obtained in the signal period.
2. The frequency is the reciprocal of the period measured.
Using the formula:
F
r e c
l -
p
|
e n o c
1 c y c l e = 4 0 jts (5 /is/div. x 8 div.)
Fig. 5 2
[EXAMPLE]
A period of 40 /xs is observed and measured. (See Fig. 52)
Assuming that SWEEP TIME/DIV indicates 5 /ts/div,
substituting the given Value:
6
Freq=1/[40x10"
] = 2 . 5 x 1 0 * = 25 kHz
While the above method relies on the measurement directly
of the period of one cycle, the frequency may also be
measured by counting the number of cycles present in a
given time period.
1. Apply the signal to the INPUT jack. Set the vertical
MODE to the channel to be used and adjusting the
various controls for a normal display. Set the VARIABLE
control to CAL position.
2. Count the number of cycles of waveform between a
chosen set of graticules in the vertical axis direction.
Using the horizontal distance between the vertical lines
used above and the SWEEP TIME/DIV, the time span
may be calculated. Multiply the reciprocal of this value
by the number of cycles present in the given time span.
If " x 10 M A G " is used multiply this further by 10.
Note that errors will occur for displays having only a few
cycles.
Using the formula:
# of cvcles x " x 10 M A G " value
Freq=
!
Horizontal distance (div) x SWEEP TIME/DIV setting
Count c y c l e s b e t w e e n this portion
Fig. 5 3
[EXAMPLE]
For the example, within 7 divisions there are 10 cycles.
The SWEEP TIME/DIV is 5 ps/div. (See Fig. 53)
Substituting the given value:
c
10
Freq=
7 (div) x 5 (ps/div)
= 285.7 kHz
Cursor measurement
1. Apply the signal to INPUT jack, setting the vertical
MODE switch to the channel to be used and adjusting
the various controls for a normal display.
VOLTS/DIV and SWEEP TIME/DIV to obtain an easily
observed display.
Set the VARIABLE to CAL.
2. Set the cursor mode to MAT.
3. Adjust the A REF cursor to the left of the points to
be measured, and the A cursor to the right.
4. Measured value is displayed in the upper part on the
screen posterior to 11 AT.
31
Advertisement
Table of Contents
