4. CRO Basics
Focussing system
Deflection system
Electron Gun
Fluorescent screen
• It consists of a filament(F), the cathode(C), and the control grid (G).
• Filament coil emits electrons, that strike the cathode.
• The cathode in turn generates the secondary electrons.
• The control grid maintained at low negative potential controls the
electron beam density.
5. CRO Basics
Focussing system
Deflection system
Electron Gun
Fluorescent screen
• It consists of a pre-accelerating anode A1, an accelerating anode A2
and a focussing anode A3.
• Anodes are hollow metallic co-axial cylinders kept at positive
potentials, maintained at gradually increasing order.
• Anodes focus the divergent electron beam and drag it forward.
6. CRO Basics
Focussing system
Deflection system
Electron Gun
Fluorescent screen
It consists of a
• pair of vertical deflection plates or Y deflection pair of parallel horizontal plates,
separated by a small distance. On application of voltage the electron beam shifts
upwards or downwards.
• Pair of horizontal deflection plates or X deflection pair of parallel vertical plates for
horizontal deflection
7. CRO Basics
Focussing system
Deflection system
Electron Gun
Fluorescent screen
It consists of a
• pair of vertical deflection plates or Y deflection pair of parallel horizontal plates,
separated by a small distance. On application of voltage the electron beam shifts
upwards or downwards.
• Pair of horizontal deflection plates or X deflection pair of parallel vertical plates for
horizontal deflection
8. CRO Basics
Focussing system
Deflection system
Electron Gun
Fluorescent screen The inner surface of the screen is coated with a conductive material called aquadag-
Aqueous Deflocculated Acheson Graphite
