Page 49 - Basics of Electrical, Electronic and Communication

276 Chapter 14. Measurements and data acquisition systems

3. The horizontal deflection system, including the time-base gener-
ator and synchronization circuitry.

4. Power supplies.

Signal to be Vertical
displayed amplifier (Volts/Div) Vertical deflection Horizontal deflection
plates
plates

Electron
Gun
Electron beam Screen

Trigger Time-base Horizontal
circuit generator amplifier (Time/Div)

Figure 14.1: Block diagram for a CRO

The waveform to be displayed is fed to the vertical deflection system
(Y-input) of the CRT. The horizontal deflection system provides the
voltage for moving the beam horizontally. It has a sawtooth genera-
tor or a time-base generator and a synchronization circuit. The time
base generator produces a sawtooth waveform (see figure 14.3(b)) for
horizontal deflection of the electron beam. The purpose of the synchro-
nization circuit is to start the horizontal sweep at a specific instant, with
respect to the waveform under observation. It synchronizes two types
of deflections so that horizontal deflection starts at the same point of
the input vertical signal each time it sweeps. In addition to the internal
sweep, there is a provision for external horizontal input (X-input). The
operation of vertical section and horizontal section are independent of
each other.
Cathode ray tube and its various components are discussed in the
following section.

276