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1 1 . FREQUENCY MEASUREMENTS
Frequency measurements are made by measuring the peri-
od of one cycle of w a v e f o r m and taking the reciprocal of
this time value a s the frequency.
Procedure:
1 . Following the proceudre described in section 5 " T i m e
M e a s u r e m e n t s " , measure the time of each c y c l e . T h e
figure obtained in the signal period.
2. T h e frequency is the reciprocal of the period measured.
Using the formula:
Freq -
j
|
p e r
o c
1 c y c l e = 4 0 /*s (5 / * s / d i v x 8 div)
Fig. 38
[EXAMPLE]
A period of 4 0 /ts is observed and measured. (See Fig. 3 8 )
Assuming that S W E E P T I M E / D I V indicates 5 jis/div,
substituting the given Value:
Freq = 1 / [ 4 0 x 1 0 - 6 ] = 2 . 5 x 1 0
While the above method relies on the measurement direct-
ly of the period of one c y c l e , the frequency may also be
measured by counting the number of c y c l e s 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 con-
trols for a normal display. Set the V A R I A B L E control to
C A L position.
2. Count the number of c y c l e s 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 S W E E P TIME/DIV, the time span may
be calculated. Multiply the reciprocal of this value by the
number of c y c l e s present in the given time span. If " x 10
M A G "
is used multiply this further by 1 0 .
Note that errors will occur for displays having only a f e w
cycles.
4
= 2 5 kHz
Using the formula:
# of c y c l e s x " x 10 M A G " value
Freq=
Horizontal distance (div) x S W E E P T I M E / D I V setting
Count cycles between this portion
Fig. 3 9
[EXAMPLE]
For the example, within 7 divisions there are 10 c y c l e s .
The S W E E P T I M E / D I V is 5 jis/div. (See Fig. 3 9 )
Substituting the given value:
10
F r e q =
7 (div) x 5 (/iS/div)
= 2 8 5 . 7 kHz
Cursor measurement (CS-5130 only)
1 . Apply the signal to INPUT jack, setting the vertical MODE
switch to the channel to be used and adjusting the vari-
ous controls for a normal display.
V O L T S / D I V and S W E E P T I M E / D I V to obtain an easily ob-
served display.
Set the V A R I A B L E to C A L .
2 . S e t the cursor mode to
3 . Adjust the A R E F 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
MAT.
—
MAT.
29
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