cathode ray tube working and its applications

1. Cathode Ray Tubes

2. How Does it Compare to Other
Monitors Now?
• Advantages: Cheaper on the market now, due to
being established longer
• Disadvantages:
• Produces x-rays; some are not blocked by lead
shield
• Disposal: have to deal with lead; illegal to just
dump in trash
• Big, bulky, power hungry (110 watts; compared to
35 watt LCDs)
• Accounts for 80% of electricity use in typical
home computer setup!

3. Basic Monitor Interface
• The basic interface between any monitor and the
computer, whether CRT or LCD, is identical. It’s
just the structure of the display that differs.
• An UXGA adapter takes digital data sent by
application programs, stores it in VRAM or some
equivalent, and converts the data from digital into
analog data for transmission to the monitor.

4. Transmission from PC to Monitor
• The display information is in analog form,
so it is send to the monitor through a VGA
cable.
• There are many signals, all of these
combined into a composite signal by the
VGA cord

5. What do you already know about
Cathode Ray Tubes?

6. Structure of Cathode Ray Tube
• “Cathode rays” in a vacuum tube. Cathode rays are high energy
electrons emitted from the heated cathode (-) of a vacuum tube

7. How Does it Work
• Electron gun is weak particle accelerator (only
electrons(-)).
• Aims electrons at phosphor screen where they
light up the image
• Small heater heats cathode (-), emits electron
cloud that is focused into an electron beam by two
anodes(+): accelerating anode and focusing anode.
• Black-and-white monitors only have one electron
gun; color monitors have three (RGB).

8. Variations of CRTs
• Metal screen filled with holes sitting just behind
phosphor layer. Electron guns each send beam
through hole to a single pixel triad of tube’s
phosphor layer.
• Aperture Grill - Looks kind of like a grill; with
lines jutting down the screen packed together in
strips
• Shadow Mask – - packed together in clusters. If
you look closely, you can see little individual dots,
known as pixels

9. Why So Big and Bulky?
• Standard cathode ray tube technology
requires a certain distance between beam
projection device and screen (kind of like
mile-long particle accelerators).

10. How Long has it Been Around?
• Invented in 1896 by Ferdinand Braun
• First used for oscilloscopes, then for
television, and finally for computers.
• Philo Farnsworth developed the
cathode ray tube that would be used
for television and other electronic
displays
• Responsible for many contributions to
physics, but this is a computer programming
class, not a physics class.

11. Where can you see it?
• Look right in front of you. They’re big and
fat; what else can they be?

12. Some Various Information
• If you work near the back of a cathode ray
computer monitor, you’ll be dosed with
more radiation than if you were working at
the front of it.
• Do not put a power magnet near a cathode
ray tube; can cause magnetization of the
shadow mask

13. The Future of CRTs
• Because CRTs now offer no real advantages
over LCD monitors, they will become
obsolete soon. The price of LCDs is already
decreasing.