A cathode ray tube

A cathode ray tube, also known as CRT or CRT, is an electron tube provided with a fluorescent screen which lights up when it is hit by the electron beam, and an articulating mechanism with which the electron beam can be controlled so that an image becomes visible.The name 'tube' is used mainly to the cathode ray tube in a television device to indicate. The name "CRT" is the abbreviation of the English name "Cathode Ray Tube '. The first cathode-ray tubes were used in the oscilloscope . The best-known application of the cathode ray tube which is as a television screen . A simpler form of a cathode ray tube is a tube indicator .



Content
[ *1 Design and function  ==Construction and operation [  edit ] == The cathode ray tube is composed of a cylindrical part (neck) with the electron gun, and a conical transition to a more or less flat screen.In the neck one finds the electron gun with the cathode therein by the electrons generates for the bundle and with so-called grids for the electron beams to focus and to converge to a point.
 * 2 Details
 * 3 Color Screens
 * 4 Configuration
 * 5 Phosphors
 * 6 Future
 * 7   Warnings

The beam then passes through a field with which it is deflected in its entirety. In an oscilloscope this field is electrostatically (see drawing).In a television display tube the field is magnetic . This field is generated by two coils that are slid externally over the neck.

The discipline that deals with bundling, deflect and otherwise manipulate electron beams, hot electron optics . ==Details [  edit ] == A cathode ray tube (CRT) is made ​​of lead-containing quartz glass and metal parts. The interior space is hermetically sealed and high vacuum pumping.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">The glass is at the front at least one centimeter thick, in the tubular part is reduced to a few millimeters. It has the flared portion on the outside like a lead coating (aquadag). On the inside there is a vapor-deposited aluminum layer in display tubes in order to dispose of the electrons from the screen. In oscilloscope tubes, this is sometimes a carbon layer. The outer layer is connected to the metal chassis of the installation concerned. (TV or monitor .) The inner layer is connected by means of a contact point in the glass wall ( electrode ) connected to the high-voltage transformer that provides the post-acceleration. With the glass as a dielectric that forms a capacitor . In the narrow tubular portion of this part is (are) arranged the electron gun of which their connecting wires through the glass wall it are brought out. The electron gun brings an oscilloscope or black and white TV tube and one electron beam in a color picture tube three electron beams on.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">In an oscilloscope, the deflection plates are placed inside the tubular portion. In a television picture tube to be used in external deflection coils instead. Either by varying the voltage between the deflection plates, or the current intensity by varying the deflection coils, the electron beam over the entire surface of the front side can be controlled. For example, a grid can be made to any point of the screen can be alleviated. Due to the electron-ray beam (s) to deflect with simultaneous variation of the beam intensity (s), an image can be built up, which is detected by the inertia of the image processing by our eyes as a complete whole. (See details in the page Television Engineering ).

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">The front portion, the faceplate, is composed of a much bigger and flatter plate of quartz glass on the inside of the phosphor is disposed.One kind of phosphor for monochrome displays, three separate phosphors (in jobs or groups RGB) for color displays.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">On the inside of this phosphor layer is a vapor-deposited layer of aluminum applied to absorb ions which otherwise because of their much larger mass than electrons, the phosphor in the long run brown discolor, so that the light output will decrease (the so-called Ion-Blot ). As ions are much heavier than electrons, they will be by the magnetic field of the deflection coils, either by the electric field between the deflection plates, to be less strongly deflected, making this discoloration occurs only in the middle of the screen. Former CRT screens, which had not yet deposited aluminum layer, had a so-called ion trap . ==Color Screens <span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;font-family:sans-serif;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[  edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] == <p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">In color displays, each pixel is composed of three phosphor dots, one for each of the colors red, green and blue. Just in front of the display screen, at a distance of about 0.5 cm, there is a perforated metal plate, the so-called shadow mask, which follows the curvature of the inner side of the front. The perforations correspond with the image points and ensure that the three electron beams from the three electron guns, each of which are at a different angle on the mask, only affect the phosphorescent point of the color concerned.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">The electron beams which the path from the shadow mask to the phosphor screen, followed by magnetic fields deflected from their direction. Due to stray magnetic fields, such as the Earth's magnetic field, the phosphor dots of the "wrong" color can be affected.Therefore tubes for each point on Earth magnetic otherwise be adjusted.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">The electron gun consists of a cathode and a plurality of metal plates with an aperture for each beam. Such platelets are in analogy withradio tubes are called grids. Within the cathode is a filament which heats the cathode to about 1000 C, so that electrons are released by the heat movement. The potential on the second plate pulls the electrons away from the cathode. Due to the voltage on the cathode and thus the potential difference with the second plate, to vary the current in the beam can be arranged. The following grates accelerate the electrons up to about 30 keV, and focus the beam. At this energy the electrons have a speed equal to about one-third the speed of light, so designers of tubes with relativistic effects must take into account. In some cathode ray tubes which focusing is dynamic, which means that the focusing depends on the position on the screen where the electrons will countries. Between electron gun and a phosphor screen prevails equipotentiaalruimte in that the screen is brought at the same potential as the last picture of the electron gun. In the equipotentaalruimte the electrons are thus no longer be accelerated, but due to the presence of a magnetic deflectieveld diffracted to a certain point on the screen. These variations of tension on the grids, as well as the timing of the deflecting electronics can produce an image that our eyes seem full screen entirely. ==<span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;font-family:sans-serif;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[Configuration  edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] == <p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">The classic configuration with three electron guns in an equilateral triangle caused problems with the converging. Modern cathode ray tubes have a configuration with three electron guns lying on an imaginary horizontal line. ==<span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;font-family:sans-serif;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[Phosphors  edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] == <p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">The fluorescent screen itself is of a material which is referred to by the term phosphor and has the following important properties: the color, and the afterglow of the light output. The color is usually green or blue for visibility when mainly pictures of the screen are taken. The color was white to black and white television screens and red, green, blue for color . The afterglow is usually short, except for radar screens .

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">Note: the designation of phosphorus has to do with the phosphorescent properties of the material and not to the chemical element phosphorus . In fact, phosphorus in the sense of aphosphorescent substance anglicism . The correct term is Dutch phosphor or phosphor. The chemical element phosphorus is called in English phosphorus, while a phosphorescent substance called phosphor. ==<span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;font-family:sans-serif;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[Future  work <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] == <p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">The cathode ray tube display as you will hardly use. Especially for larger screen sizes, they take a lot of space, are very heavy and require very high voltages, which in turn harmful x-ray radiation has the effect. Instead of an oscilloscope is increasingly used a measuring device via a USB - interface with a computer is connected. The computer tester can be controlled and the results can be made visible. The radar tube has been almost everywhere replaced by a computer. And increasingly, both computers and televisions have a thin LCD (Liquid Crystal Display) or plasma. ==<span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;font-family:sans-serif;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[Warnings  edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] ==
 * Because a cathode ray tube in a vacuum prevails, exists implosion in case of damage of the tube.
 * Cathode ray tubes operate at very high voltages, the picture tube of a television is that around 30,000 volts . This high voltage may be present for a long time after switching off the device. Working on such devices require expertise; Cathode ray tubes are not suitable to experiment with.