This post is part of the series Chapter-1 Applied Electronics
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There are two section in block diagram, vertical section and horizontal section.
- Signal to be observed on screen, is connected to y-input of CRO.
- The input signal is attenuated or amplified depending on the requirement. We can manually adjust this using Volt/div setting knob.
- Then the signal passes through delay line so that the signal reaches after about 0.25µsec on vertical deflection plates.
- So with changing polarity of signal at y-input the beam deflects vertically.
- A sample of signal is passed to trigger circuit in horizontal section of CRO.
- Trigger circuit receives the sample and triggers the time base generator (TBG) i.e. sawtooth oscillator.
- Time base generator consists of UJT oscillator to produce sawtooth waves. Frequency can be controlled using
- Time/div control knob of front panel. The output of TBG is fed to horizontal amplifier.
- The gain of horizontal amplifier is larger than vertical amplifier because, horizontal deflection sensitivity is smaller than vertical. Horizontal amplifier consists of two amplifier units: positive & negative. Its output produces two different sawtooth waves which are 180º phase inverted with respect to each other. They are fed to horizontal deflection plates.
- The blanking circuit is connected to time base generator. When sawtooth reaches to peak, the blanking circuit triggers and feeds a high negative voltage to control grid. This stops the emission of electrons from its center hole.
- Thus the beam is blanked for short time.