RCA 54-45 Manual page 28

NOTE 2 : At low sweep frequencies , flickering of the pattern is normal due to the slow writing
speed of the spot and the persistence of the screen, which together are insufficient to
cause the motion to blend into a fixed image.
SEC TION III. APPLICATIONS
GENERAL: The oscilloscope is an instrument designed for viewing electrical oscillations and
transients . Phenomena having a repetition rate from a few cycles per second to several megacycles
per second may be displayed on a 'scope.
WAVE FORM INVESTIGATION: When the output of the internal sweep generator is fed to the hori­
zontal channel, the pattern on the screen is actually a graph showing the variation with time of the
instantaneous amplitude of the signal applied to the vertical channel. The sweep frequency is usually
a sub- harmonic of the signal frequency, so that several complete cycles of the signal are displayed
on the screen.
DISPLAY OF WAVE FORMS : Displaying a waveform means obtaining a picture that shows how the
amplitude of the signal under observation varies with time. It is generally most convenient to use a
time-base signal that varies linearly with time, so that equal intervals of time are represented on the
screen by equal intervals of distance along the same axis . The sawtooth output of the sweep generator
gives such a time-base on the horizontal axis , the time (in seconds) represented by the overall hori­
zontal deflection being equal to the reciprocal of the sweep frequency (in cycle per second) .
If the frequency of the observed signal is equal to the sweep frequency, one complete cycle will
be observed on the screen. If the frequency of the applied signal is twice the sweep frequency, two
complete cycles will be obtained on the screen and so on. Fig. 1 is a proj ection drawing of a sine
wave applied to the vertical plates and sawtooth wave of the same frequency applied to the horizontal
plates. Fig. 2 is a proj ection drawing showing the resultant pattern when the frequency of the sawtooth
is one-half that employed in Fig. 1.
In these figures, points that occur simultaneously are numbered the same . The circle represents
the tube screen. If simultaneous proj ections were drawn from every point on each wave, the inter­
sections would trace out the sine waves shown in the circles. The sections of sawtooth between 1 and
4 in Fig. 1 and between 1 and
duced. The sections of the sawtooth between 4 and 5 in Fig. 1 and between
sections during which the beam is returned very rapidly to the starting point at the left-hand side of
the screen.
Figure 1 . 1 Cycle o f Sine Wave vs . Sawtooth
in Fig. 2 are the sweep sections during which the displays are pro­
9
I
I
I
I
i
TI M E 1
1
SEC ..
6 0
I
1
T I M E -
Figure 2. 2 Cycles of Sine Wave vs . Sawtooth
27
and 10 in Fig. 2 are the
9
I
I
I
I
t
t lO
TI M E
1
3 0 SEC.