The different types of sweeps are as follows:
- Recurrent Sweep - When the saw tooth, being an AC voltage,
alternates rapidly, the display also occurs repetitively, giving out
a lasting image. This operation is called recurrent sweep.
- Single Sweep - The signal under study produces a trigger signal,
which in turn produces a single sweep.
- Driven Sweep - The saw tooth oscillator is a free running generator
when operated independently. There is a chance that the sweep cycle
may start after the signal cycle, thereby missing a part of the
signal. Driven sweep removes this possibility because it is fixed by
the signal itself. The sweep and signal cycles start at the same
- Triggered Sweep - In a recurrent mode, the pattern is repeated again
and again. In this mode the voltage rises to a maximum and then
suddenly falls to a minimum. Electron beam moves slowly from left to
right, retraces rapidly to the left and the pattern is repeated. The
horizontal sweep action takes place whether the input signal is
applied to the oscilloscope or not, and a horizontal line is
displayed on the scope screen. A triggered sweep, on the other hand,
does not start unless initiated by a trigger voltage, generally
derived from an incoming signal. A triggered scope does not use a
continuous or recurrent sweep, but uses a mono stable multivibrator
which is in its off state until a trigger pulse arrives; hence there
is no deflection on the screen.
- Intensity Modulation - In some applications, an AC signal is applied
to the control electrode of the CRT. This causes the intensity of
the beam to vary in step with signal alternations. As a result, the
trace is brightened during the +ve half cycles and diminished or
darkened during –ve half cycles. This process is called intensity
modulation or Z-axis modulation (in contrast to X-axis for
horizontal and y-axis for vertical). It produces bright segments or
dots on the trace in response to positive peak or dim segments or
holes in response to negative peaks.