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Describe various types of sweeps used in CRO
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The different types of sweeps are as follows:

  1. 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.
  2. Single Sweep - The signal under study produces a trigger signal, which in turn produces a single sweep.
  3. 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 time.
  4. 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.
  5. 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.
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