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MONITORS IN SUMMARY

 

MONITORS

MONITOR IS A PRIMARY OUTPUT DEVICE.  IT DISPLAYS ALL CURRENT PROCESS APPLICATION AND DATA I.E. RUNNING INSIDE A COMPUTER SYSTEM.  A STANDARD MONITOR USES AN ANALOG , VGA INTERFACE WHICH PLUGS INTO TP15 PIN VGA CONNECTOR TO THE MOTHERBOARD.

 

 THERE ARE TWO TYPES OF MONITOR TECHNOLOGY AVAILABLE TO THE MARKET.

HERE ARE THOSE

 

CATHODE RAY TUBE (CRT)

THIS MONITOR IS FADING IN POPULARITY BUT STILL IN WIDESPREAD USE WITH OLDER COMPUTER SYSTEMS. IT IS ANALOG STANDARD MONITOR. A CRT USES A PICTURE TUBE THAT WAS USED IN OLDER TUBE BASED TV SETS.


 

THE NARROW END OF PICTURE TUBE CONTAINS AN ELECTRON GUN.  IT EMITS 3 ELECTRON BEAMS.  ONE EACH FOR RED, GREEEN, BLUE LIGHT.  THE FRONT END OF THE PICTURE TUBE IS COATED WITH PHOSPHOROUS. 

 

WHEN THE ELECTRON HITS PHOSPHOROUS COATING IT STARTS TO GLOW.  JUST BEFORE THE PHOSPHOROUS COATING A METAL PLATE CALLED SHADOW MASK IS USED TO DIVIDE THE IMAGE CREATED BY THE ELECTRON GUN INTO RED, GREEN AND BLUE PIXELS ON STRIPS THAT FORM THE IMAGE. 

 

SHADOW MASK USES ON OF THREE TECHNOLOGIES.  A PHOSPHOUR TRIAD, AN APERTURE GRILL, A SLOTTED MASK.  CRT MONITORS ARE BULKY TAKES MORE DISK SPACE,   CONSUMES MORE POWER AND EMITS MORE HEAT.  CRT MONITOR WAS AVAILABLE FROM 15 INCH TO 19 INCH SIZE.  IT USES VGA CONNECTOR TO ATTACH WITH A CPU

 

LCD AND LED SCREENS

 

THE MOST POPULAR MONITOR IN TODAY MARKET IS LED MONITOR SUPPRESED LCD MONITORS.  BECAUSE IT GIVES BETTER COLOUIR QUALITY, WIDE VIEWING ANGLE AND CONSUMES LESS POWER.  


 

IT USES LIQUID CRYSTAL CELLS TO POLARIZE THE LIGHT.   LCD MONITORS USES FLUOROSCENT LAMP AND LED MONITORS USES LED LAMPS FOR BAKCLIGHTING .  THIS DISPLAY USES AN ARRAY OF TRANSISTORS TO CONTROL EACH CELL.

 

VARIATION ARE THE COLOUR BIT, RESPONSE TIME  AND THE REFRESH RATE.   THIS MONITORS COMES WITH TWO TYPES OF TRANSISTOR TECHNOLOGY 1) PASSIVE MATRIX 2) ACTIVE MATRIX

 

PASSIVE MATRIX

 


A PASSIVE MATRIX DISPLAY DOESNOT HAVE A DEDICATED TRANSISTOR FOR EACH PIXEL OR SUB PIXEL,  BUT INSTEAD A MATRIX OF CONDUCTIVE TRACES.  IN SIMPLIFIED TERMS FOR A SINGLE PIXEL WHEN THE DISPLAY  IS INSTRUCTED TO CHANGE THE CRYSTAL LINE ALIGNMENT FOR A PARTICULAR PIXEL.

 

IT SENDS A SIGNAL ACROSS THE X AND Y COORDINATE TRACES THAT INTERSECT AT THAT PIXEL, THUS TURNING IT ON.  A 1366 X 768 RESOLUTION MONITOR CONTAINS 1366  TRANSISTOR AT THAT HORIZONTAL EDGE AND 768 TRANSISTORS AT THE VERTICAL EDGE.

 

THE VIEWING ANGLE IS A MOST UNCONSIDERABLE ISSUE OF A PASSIVE MATRIX DISPLAY.  THE PICTURE QUALITY IS MUDDY BECAUSE THE CONDUCTIVE TRACES SOMETIMES EFFECTS THE NEIGHBOURING IXELS OF A TARGET PIXEL

 

THE ONE ADVANTAGE OF PASSIVE MATRIX IS IT ONSUMES LESS POWER COMPARING TO ACTIVE MATRIX DISPLAY.

 

DUAL SCAN DISPLAY

 


A DUAL SCAN IS A VARIATION OF THE PASSIVE METRIC DISPLAY.  THE CLASSIC PASSIVE MATRIX SCREEN IS SPLIT IN HALF TO IMPLEMENT A DUAL SCAN DISPLAY.  EACH HALF OF THE DISPLAY IS REFRESHED SEPERATELY LEADING TO INCREASED QUALITY.

 

ALTHOUGH DUAL SCAN IMPROVES THE QUALTY OF REFRESH RATE BUT IT CANNOT RIVAL THE QUALITY PRODUCED BY ACTIVE MATRIX.

 

ACTIVE MATRIX

 

THIS SCREEN IS MADE OF SEVERAL INDEPENDENT LCD OR LED PIXELS.  A TRANSISTOR AT EACH PIXEL LOCATION, WHEN SWITCHED AMONG VARIOUS LEVELS.  ACTIVATES TWO OPPOSING ELECTRODES THAT ALIGH THE PIXELS CRYSTALS AND ALTER THE PASSAGE OF LIGHT AT THAT LOCATION TWO PRODUCE MILLIONS OF COLOUR SHADES.  THIS TYPE OF DISPLAY IS VERY CRISP AND EASY TO LOOK FROM ANY ANGLE.

 

IT DOESN’T REQUIRE AN SCAN REFRESHING TO MAINTAIN AN IMAGE, BECAUSE REANSISTORS CONDUCT CURRENT ONLY IN ONE DIRECTION AND THE PIXELS ACT LIKE A CAPACITOR BY HOLDING ITS CHARGE UNTIL IT IS REFRESHED

 

HIGHER REFRESH RATES ESULTS IN BETTER VIDEO OR GAING PERFORMANCE NOT FOR STILL IMAGE.   THE MAJOR DISADVANTAGE OF ACTIVE MATRIX SCREEN THAT IT REQUIRES MORE POWER TO OPERATE ALL TRANSISTOR.   EVEN IF THE BACKLIGHT IS TURNED OF THE SCREEN CAN STLL CONSUME POWER AT AN ALARMING RATE. 

 

ANOTHER PROBLEM WITH ACTIVE MATRIX IS LIGHT BLEED.

 

THANKS FOR READING.  I HOPE YOU LIKED IT.

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