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Cutaway rendering of a color CRT:
1. Three Electron guns (for red, green, and blue phosphor dots)
2. Electron beams
3. Focusing coils
4. Deflection coils
5. Anode connection
6. Mask for separating beams for red, green, and blue part of displayed image
7. Phosphor layer with red, green, and blue zones
8. Close-up of the phosphor-coated inner side of the screen
Magnified view of a shadow mask color CRT
Magnified view of an aperture grille color CRT
.The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, used to create images in the form of light emitted from the fluorescent screen.^ Source means the focal spot of the x-ray tube.
  • Electronic Code of Federal Regulations: 10 February 2010 13:013 UTC ecfr.gpoaccess.gov [Source type: Reference]

^ The cathode of the tube is horizontal (when the tube is vertical) instead of vertical, and only the electrons emitted upwards are used.
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^ Non-image-intensified fluoroscopy means fluoroscopy using only a fluorescent screen.
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The image may represent electrical waveforms (oscilloscope), pictures (television, computer monitor), radar targets and others.
.The CRT uses an evacuated glass envelope which is large, deep, heavy, and relatively fragile.^ These tubes were given two-digit identifying numbers, and used the graceful ST shouldered glass envelopes.
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.Display technologies without these disadvantages, such as flat plasma displays, liquid crystal displays, DLP, OLED have replaced CRTs in many applications and are becoming increasingly common as costs decline.^ Without these forces, solids and liquids would act as gases.

Contents

History

A common CRT used in computer monitors and television sets
.The earliest version of the CRT was invented by the German physicist Ferdinand Braun in 1897 and is also known as the Braun tube.^ Development of the Cathode Ray Tube by Ferdinand Braun.

[1] .It was a cold-cathode diode, a modification of the Crookes tube with a phosphor-coated screen.^ An electron tube containing a cold cathode.
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^ Cold-cathode gas discharge tubes.
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^ Some cathode-ray tubes, made for computer terminals Oscilloscopes , and Television receivers, can produce multiple beams of electrons and have phosphor screens that can display more than one color.

.In 1907, Russian scientist Boris Rosing used a CRT in the receiving end of an experimental video signal to form a picture.^ CHANNELIZED RECEIVER - A SIGINT receiver which uses multiple parallel channels to filter, amplify, and detect incoming emitter signals.

^ COMPANDING - The process of compressing (limiting the dynamic range of) a transmitted signal and then restoring (expanding) it at the receiving end so as to improve overall SIGNAL-TO-NOISE performance.

^ The CRO uses a CRT to produce a graph of how an input signal voltage varies with time.

.He managed to display simple geometric shapes onto the screen, which marked the first time that CRT technology was used for what is now known as television.^ RCA / GE 2" Electrostatic CRT. Used, Dynamically tested good, LOOKS GOOD, very bright, no burns or marks.
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^ Almost all televisions sold are now flat LCD and Plasma screens.

^ The 12EK6 (also known as 12DZ6 and 12EA6) is a screen-grid pentode for low-voltage use.
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[2]
The first cathode ray tube to use a hot cathode was developed by John B. Johnson (who gave his name to the term Johnson noise) and Harry Weiner Weinhart of Western Electric, and became a commercial product in 1922.

Overview

.A cathode ray tube is a vacuum tube which consists of one or more electron guns, possibly internal electrostatic deflection plates, and a phosphor target.^ For plural phosphor target tube .
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^ For cathode-ray tube having plural targets .
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^ Cathode-ray deflections circuits .
  • Class Schedule for Class 315 ELECTRIC LAMP AND DISCHARGE DEVICES: SYSTEMS 10 February 2010 13:013 UTC www.uspto.gov [Source type: Reference]

[2] .In television sets and computer monitors, the entire front area of the tube is scanned repetitively and systematically in a fixed pattern called a raster.^ This is called raster scanning .

^ A predetermined pattern of scanning lines which provides substantially uniform coverage of an area.
  • Vacuum Tube Technology: A Perspective Circa 1950 10 February 2010 13:013 UTC www.pentodepress.com [Source type: Reference]

^ A cathode-ray tube used to produce an image by variation of the beam intensity as the beam scans a raster.
  • Vacuum Tube Technology: A Perspective Circa 1950 10 February 2010 13:013 UTC www.pentodepress.com [Source type: Reference]

.An image is produced by controlling the intensity of each of the three electron beams, one for each additive primary color (red, green, and blue) with a video signal as a reference.^ This produces a narrow beam of electrons.

^ In colour TV there are three electron guns, each one able to activate only one of the primary colours (red, green or blue) on the screen.

^ Some cathode-ray tubes, made for computer terminals Oscilloscopes , and Television receivers, can produce multiple beams of electrons and have phosphor screens that can display more than one color.

[3] .In all modern CRT monitors and televisions, the beams are bent by magnetic deflection, a varying magnetic field generated by coils and driven by electronic circuits around the neck of the tube, although electrostatic deflection is commonly used in oscilloscopes, a type of diagnostic instrument.^ An assembly producing a magnetic field for focusing an electron beam.
  • Vacuum Tube Technology: A Perspective Circa 1950 10 February 2010 13:013 UTC www.pentodepress.com [Source type: Reference]

^ A method of focusing an electron beam by the action of a magnetic field.
  • Vacuum Tube Technology: A Perspective Circa 1950 10 February 2010 13:013 UTC www.pentodepress.com [Source type: Reference]

^ Then a known magnetic field was applied and the position of the deflected beam noted.

[3]
Electron gun

Oscilloscope CRTs

.In oscilloscope CRTs, electrostatic deflection is used, rather than the magnetic deflection commonly used with television and other large CRTs.^ RCA / GE 2" Electrostatic CRT. Used, Dynamically tested good, LOOKS GOOD, very bright, no burns or marks.
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^ Magnetic fields are used to deflect the electron beam in this CRT, since the magnetic fields allow for a wider-angle beam than would be possible with electric fields from charged plates.

^ Toshiba 5" Circular Flat Electrostatic CRT, used in Bell and Howell and other lower frequency scopes, P31 high intensity phosphor.
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.The beam is deflected horizontally by applying an electric field between a pair of plates to its left and right, and vertically by applying an electric field to plates above and below.^ The voltage signal to be measured is applied to the vertical deflection plates.

^ Then a known magnetic field was applied and the position of the deflected beam noted.

^ The magnitude, E , of the electric field between the plates can be shown to be: .

[4][5][6]

Phosphor persistence

Various phosphors are available depending upon the needs of the measurement or display application. .The brightness, color, and persistence of the illumination depends upon the type of phosphor used on the CRT screen.^ Shown lit running a Forbes CRT clock, which could use a bit more HV for better brightness on this tube.
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^ The maximum kinetic energy of emitted electrons was found to depend on the frequency of the light used and the type of surface.

^ The electrodes in the CRT's electron gun produce a narrow beam of electrons, which produces a bright spot on the CRO's fluorescent screen.

.Phosphors are available with persistences ranging from less than one microsecond to several seconds.^ The commercial consists of four frames (each costing $945) and lasts less than a second.

^ Pulsed mode means operation of the x-ray system such that the x-ray tube current is pulsed by the x-ray control to produce one or more exposure intervals of duration less than one-half second.
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^ Many tubes are available for less than $5.00 each, a good value, taking care to avoid the ones in demand for antique radios, musical instruments and hi-fi amplifiers.
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[7] For visual observation of brief transient events, a long persistence phosphor may be desirable. .For events which are fast and repetitive, or high frequency, a short-persistence phosphor is generally preferable.^ Has neck deflection connections, so it can run at very high frequency with fast writing speed.
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^ Using a FAST FOURIER TRANSFORM (FFT) chip, the receiver instantaneously monitors 2 megahertz of BANDWIDTH in the high frequency (HF) spectrum.

[8]

Microchannel plate

.When displaying fast one-shot events the electron beam must deflect very quickly, with few electrons impinging on the screen; leading to a faint or invisible display.^ Acceleration of the beam electrons after deflection.
  • Vacuum Tube Technology: A Perspective Circa 1950 10 February 2010 13:013 UTC www.pentodepress.com [Source type: Reference]

^ Some cathode-ray tubes, made for computer terminals Oscilloscopes , and Television receivers, can produce multiple beams of electrons and have phosphor screens that can display more than one color.

^ To form the screen display, or image, the electron beam is deflected in the vertical and horizontal directions either by the electrostatic effect of electrodes within the tube or by magnetic fields produced by coils located around the neck of the tube.

.Oscilloscope CRTs designed for very fast signals can give a brighter display by passing the electron beam through a micro-channel plate just before it reaches the screen.^ Some cathode-ray tubes, made for computer terminals Oscilloscopes , and Television receivers, can produce multiple beams of electrons and have phosphor screens that can display more than one color.

^ To form the screen display, or image, the electron beam is deflected in the vertical and horizontal directions either by the electrostatic effect of electrodes within the tube or by magnetic fields produced by coils located around the neck of the tube.

^ Useful beam means the radiation which passes through the tube housing port and the aperture of the beam-limiting device when the exposure switch or timer is activated.
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.Through the phenomenon of secondary emission this plate multiplies the number of electrons reaching the phosphor screen, giving a significant improvement in writing rate (brightness), and improved sensitivity and spot size as well.^ The electron beam leaves a bright spot wherever it strikes the screen.

^ The secondary electrons fall into the screen, to which they are attracted.
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^ It happens that speedy electrons colliding with the plate knock out secondary electrons.
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[9][10]

Graticules

Most oscilloscopes have a graticule as part of the visual display, to facilitate measurements. .The graticule may be permanently marked inside the face of the CRT, or it may be a transparent external plate.^ Flat face allows easy use of a graticule or other markings.
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^ On equipment having all or some of these conditions of operation at fixed values, this requirement may be met by permanent markings.
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^ On equipment having fixed technique factors, this requirement may be met by permanent markings.
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External graticules are typically made of glass or acrylic plastic. An internal graticule provides an advantage in that it eliminates parallax error. .Unlike an external graticule, an internal graticule can not be changed to accommodate different types of measurements.^ The cathode ray oscilloscope (CRO) is used to measure potential differences that change too rapidly with time to be measured using a simple voltmeter.

^ Unlike transistors, tubes of different types can have quite different (though similar) characteristics, so characteristic curves are much more important.
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[11] .Oscilloscopes commonly provide a means for the graticule to be side-illuminated, which improves its visibility when used in a darkened room or when shaded by a camera hood.^ Source-skin distance —(1) X-ray systems designed for use with an intraoral image receptor shall be provided with means to limit the source-skin distance to not less than: .
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^ Positive means 2 shall be provided to ensure that at least the minimum filtration needed to achieve the above beam quality requirements is in the useful beam during each exposure.
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^ Radiographic equipment designed for use with an intraoral image receptor shall be provided with means to limit the x-ray beam such that: .
  • Electronic Code of Federal Regulations: 10 February 2010 13:013 UTC ecfr.gpoaccess.gov [Source type: Reference]

[12]

Color CRTs

Spectra of constituent blue, green and red phosphors in a common CRT
.Color tubes use three different phosphors which emit red, green, and blue light respectively.^ Since the heater current is 1.1 A, the tube is obviously designed to use higher plate currents, and its parameters will be somewhat different in these regions.
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^ Used NO BOX, NOT full brightness (about 60% compared to a new tube), same electrically as DB7-12C, but P31 fast phosphor.
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^ When he used a bent tube, the most intense green glow appeared on the part of the tube opposite the cathode.

They are packed together in stripes (as in aperture grille designs) or clusters called "triads" (as in shadow mask CRTs).[13] .Color CRTs have three electron guns, one for each primary color, arranged either in a straight line or in a triangular configuration (the guns are usually constructed as a single unit).^ A grid that is interposed between two positive electrodes (usually the screen grid and the plate), primarily to reduce the flow of secondary electrons from one electrode to the other.
  • Vacuum Tube Technology: A Perspective Circa 1950 10 February 2010 13:013 UTC www.pentodepress.com [Source type: Reference]

^ CATHODE - In a VACUUM TUBE , the electrode through which a primary stream of electrons is generated, usually through THERMIONIC EMISSION .

^ This allows the electron beam to be deflected from the straight-line trajectory with which it leaves the electron gun.

A grille or mask absorbs the electrons that would otherwise hit the wrong phosphor.[14] .A shadow mask tube uses a metal plate with tiny holes, placed so that the electron beam only illuminates the correct phosphors on the face of the tube.^ A famous beam power tube was the type 807, a graceful large tube with an ST envelope and a plate cap, shown in the photograph at the right.
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^ Since the heater current is 1.1 A, the tube is obviously designed to use higher plate currents, and its parameters will be somewhat different in these regions.
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^ Used NO BOX, NOT full brightness (about 60% compared to a new tube), same electrically as DB7-12C, but P31 fast phosphor.
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[13] .Another type of color CRT uses an aperture grille to achieve the same result.^ The other exciting feature of semiconductors is that when a crystal is produced consisting of p-type and n-type material in contact, the resulting p-n junction has the following useful properties: .

^ The heater takes 2.5V at 1.75A, so it can use the same transformer as the type 82.
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[14]

Convergence in color CRTs

.The three beams in color CRTs would not strike the screen at the same point without convergence calibration.^ Magnetic fields are used to deflect the electron beam in this CRT, since the magnetic fields allow for a wider-angle beam than would be possible with electric fields from charged plates.

^ The electrodes in the CRT's electron gun produce a narrow beam of electrons, which produces a bright spot on the CRO's fluorescent screen.

^ CATHODE RAY TUBE (CRT) - A display device in which controlled electron beams are used to present alphanumeric or graphical data on an electroluminescent screen.

Instead, the set would need to be manually adjusted to converge the three color beams together to maintain color accuracy.[15]

Degaussing

.Most CRT television sets and computer monitors have a built-in degaussing (demagnetizing) coil, which upon power-up creates a brief, alternating magnetic field which decays in strength over the course of a few seconds.^ Magnetic fields are used to deflect the electron beam in this CRT, since the magnetic fields allow for a wider-angle beam than would be possible with electric fields from charged plates.

^ Hertz reasoned that the spark discharge oscillating backwards and forwards between the brass balls set up changing electric and magnetic fields that propagated as an electromagnetic wave , as postulated by Maxwell.

^ Two pairs of magnetic field coils lie on either side of the neck of the picture tube.

This degaussing field is strong enough to remove most cases of shadow mask magnetization.[16]

Vector monitors

.Vector monitors were used in early computer aided design systems and in some late-1970s to mid-1980s arcade games such as Asteroids.^ COMPUTER GENERATED FORCE (CGF) - A computer system that generates AGENT s in a military simulation; it can be used with trainees in simulators fighting virtual battles, or can be run autonomously for planning of tactics.

^ Source-skin distance —(1) X-ray systems designed for use with an intraoral image receptor shall be provided with means to limit the source-skin distance to not less than: .
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^ The early digital computers, such as the IBM 850, used vacuum tubes.
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[17] They draw graphics point-to-point, rather than scanning a raster.

CRT resolution

Dot pitch defines the maximum resolution of the display, assuming delta-gun CRTs. .In these, as the scanned resolution approaches the dot pitch resolution, moiré appears, as the detail being displayed is finer than what the shadow mask can render.^ Appear to be high resolution avionics displays, Thomas Electronics is HERE .
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[18] Aperture grille monitors do not suffer from vertical moiré, however, because their phosphor stripes have no vertical detail. .In smaller CRTs, these strips maintain position by themselves, but larger aperture grille CRTs require one or two crosswise (horizontal) support strips.^ The deflection system consists of two sets of parallel plates, one set in the horizontal plane, and the other in the vertical plane.

^ A grid that is interposed between two positive electrodes (usually the screen grid and the plate), primarily to reduce the flow of secondary electrons from one electrode to the other.
  • Vacuum Tube Technology: A Perspective Circa 1950 10 February 2010 13:013 UTC www.pentodepress.com [Source type: Reference]

^ The relation, usually represented by a graph, between the voltages of two electrodes, with the current to one of them as well as all other voltages maintained constant.
  • Vacuum Tube Technology: A Perspective Circa 1950 10 February 2010 13:013 UTC www.pentodepress.com [Source type: Reference]

[19]

Gamma

.CRTs have a pronounced triode characteristic, which results in significant gamma (a nonlinear relationship in an electron gun between applied video voltage and light intensity).^ The resulting potential difference across the junction is proportional to the intensity of the light.

^ The brightness of the image on the screen is controlled by the signal voltages applied to the grid in the electron gun of the picture tube.

^ A change in voltage Δv is applied to the input, and a change in current Δi results.
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[20]

Other types of CRTs

Cat's eye

.In better quality tube radio sets a tuning guide consisting of a phosphor tube was used to aid the tuning adjustment.^ Used NO BOX, NOT full brightness (about 60% compared to a new tube), same electrically as DB7-12C, but P31 fast phosphor.
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^ This was a large power demand for a battery radio, especially when several such tubes were used.
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^ Don't confuse it with the cathode-ray tube that uses a guided electron beam for oscilloscopes and TV receivers.
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.This was also known as a "Magic Eye" or "Tuning Eye". Tuning would be adjusted until the width of a radial shadow was minimized.^ When you adjusted the tuning dial, the dark sector in the green glow of the eye contracted as you tuned in a strong station, and you tried to make the dark sector as small as possible.
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^ Adjust the signal carrier frequency until the tuned circuit resonates; in my case, this was 500 kHz.
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.This was used instead of a more expensive electromechanical meter, which later came to be used on higher-end tuners when transistor sets lacked the high voltage required to drive the device.^ Both demand fairly high voltages and are expensive.
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^ The voltage is controlled manually here, but in practice a triode with a 510k plate resistor is used instead, operated by the AVC voltage on the grid.
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^ COOPERATIVE ANGLE JAMMING (CAJ) - A jamming technique requiring the cooperative use of two or more aircraft to deceive hostile radar-guided missiles.

[21]

Charactrons

.Some displays for early computers (those that needed to display more text than was practical using vectors, or that required high speed for photographic output) used Charactron CRTs.^ COOPERATIVE ANGLE JAMMING (CAJ) - A jamming technique requiring the cooperative use of two or more aircraft to deceive hostile radar-guided missiles.

^ Magnetic fields are used to deflect the electron beam in this CRT, since the magnetic fields allow for a wider-angle beam than would be possible with electric fields from charged plates.

^ A small receiver required something less than a watt output for adequate volume, a larger receiver perhaps 5 W. Public address systems often required more.
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.These incorporate a perforated metal character mask (stencil), which shapes a wide electron beam to form a character on the screen.^ As these atoms come together to form the crystal lattice, some of the weakly bound electrons are freed from their atoms by the energy released in binding.

^ Thus, the electron beam zigzags down the screen from the top left corner to the bottom right and then repeats its motion.

^ Beam-forming electrodes, as shown in the sketch on the right, connected to the cathode shaped the electron stream into a dense beam on either side of the cathode.
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.The system selects a character on the mask using one set of deflection circuits, but that causes the extruded beam to be aimed off-axis, so a second set of deflection plates has to re-aim the beam so it is headed toward the center of the screen.^ Note that the Miller capacitance between grid and plate still has its effect multiplied by the gain, and also that the circuit is not a cathode follower at all, though it looks like one.
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^ Magnetic fields are used to deflect the electron beam in this CRT, since the magnetic fields allow for a wider-angle beam than would be possible with electric fields from charged plates.

^ A component necessary for compliance of the system with applicable provisions of this subchapter but which may be interchanged with similar compatible components without affecting the system's compliance, such as one of a set of interchangeable beam-limiting devices; or .
  • Electronic Code of Federal Regulations: 10 February 2010 13:013 UTC ecfr.gpoaccess.gov [Source type: Reference]

A third set of plates places the character wherever required. The beam is unblanked (turned on) briefly to draw the character at that position. .Graphics could be drawn by selecting the position on the mask corresponding to the code for a space (in practice, they were simply not drawn), which had a small round hole in the center; this effectively disabled the character mask, and the system reverted to regular vector behavior.^ A graphical presentation of the sensitivity profile, at the location corresponding to the center location of the dosimetry phantom, for each selectable nominal tomographic section thickness for which the dose profile is given according to paragraph (c)(2)(iv) of this section.
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^ Sorry, we can't safely send individual small parts in a regular letter envelope, they get destroyed by the automated handling equipment.
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Charactrons had exceptionally-long necks, because of the need for three deflection systems.[22][23]

Nimo

Nimo tube BA0000-P31
.Nimo was the trademark of a family of very small non standard CRTs manufactured by Industrial Electronics Engineers with 10 electron guns, which shaped the electron beam as digits, with a similar principle as the charactron.^ Magnetic fields are used to deflect the electron beam in this CRT, since the magnetic fields allow for a wider-angle beam than would be possible with electric fields from charged plates.

^ Beam-forming electrodes, as shown in the sketch on the right, connected to the cathode shaped the electron stream into a dense beam on either side of the cathode.
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^ This enables the intensity of the electron beam to be controlled the more negative the grid, the fewer electrons are emitted from the electron gun and the less the brightness of the spot on the end of the tube.

.They were intended as single digit, simple displays, or as 4 or 6 digits by means of a special magnetic deflection system.^ The CT x-ray system shall be provided with the means to display these images on the image display device.
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^ He observed that the rays were deflected by the magnetic field as if they were negatively charged particles .

^ Yet cathode rays were deflected by a magnetic field as if they were negatively charged particles.

.Having only 3 electrode types (a filament, an anode and 10 different grids), the driving circuit for this tube was very simple, and as the image was projected on the glass face, it allowed a much wider viewing angle than for example nixie tubes which Nimo tried to replace.^ Circuits control grid-cathode circuit of tube .
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^ Tube-type circuit .
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^ A six-electrode electron tube containing an anode, a cathode, a control electrode, and three additional electrodes that are ordinary grids.
  • Vacuum Tube Technology: A Perspective Circa 1950 10 February 2010 13:013 UTC www.pentodepress.com [Source type: Reference]

[24]

Zeus Thin CRT Displays

.In the late 1990's and early 2000's Philips Research Laboratories experimented with a type of thin CRT known as the Zeus display which contained CRT-like functionality in a flat panel.^ Telefunken 5" Round Electrostatic CRT, PDA type, flat face NIB. General purpose scope and display tube.
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^ Philips/Miniwatt 4" Round Electrostatic CRT, PDA, high frequency type with neck deflection plate connections, flat face, filament checked OK, new loose packed tube.
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^ Philips 5" Rectangular, flat face Electrostatic CRT, LOOKS VERY GOOD. Removed from Philips PM3311 digital storage scope, excellent condition, P31 Phosphor.
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[25][26][27][28][29][30] The devices were demonstrated but never marketed.

The future of CRT technology

Demise

.The demand for CRT screens has been falling rapidly,[31] and producers are responding to this trend.^ The electrodes in the CRT's electron gun produce a narrow beam of electrons, which produces a bright spot on the CRO's fluorescent screen.

For example, in 2005 Sony announced that they would stop the production of CRT computer displays. .It has been common to replace CRT-based televisions and monitors in as little as 5–6 years, although they generally are capable of satisfactory performance for a much longer time.^ All these tubes, once so common and useful, have been totally replaced by the much cheaper and smaller semiconductor diode.
  • Electronics 27 10 February 2010 13:013 UTC www.du.edu [Source type: FILTERED WITH BAYES]

^ The horizontal time base moves the spot from left to right across the screen, while the vertical time base moves the spot down the screen at a much slower rate.

^ Although power triodes were replaced by power pentodes and beam power tubes in the 1930's, they remained as favorites in hi-fi amplifiers.
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The end of most high-end CRT production in the mid 2000s (including high-end Sony and Mitsubishi product lines) means an erosion of the CRT's capability.[32][33] .Samsung did not introduce any CRT models for the 2008 model year at the 2008 Consumer Electronics Show and on February 4, 2008 Samsung removed their 30" wide screen CRTs from their North American website and has not replaced them with new models.^ NATIONAL 3" wide flat face electrostatic CRT. This is a 3RP1A with added mu-metal magnetic sheld (easily removed if not wanted, taped in place), an exact replacement for most 3RP1A applications.
  • Sphere's Cathode Ray Tube - CRT Page - Alphabetic prefix part numbers 10 February 2010 13:013 UTC www.sphere.bc.ca [Source type: FILTERED WITH BAYES]

^ In March, Walter Cronkite steps down after 19 years of anchoring the CBS evening news and is replaced by Dan Rather.

^ CATHODE RAY TUBE (CRT) - A display device in which controlled electron beams are used to present alphanumeric or graphical data on an electroluminescent screen.

[34] This demise in the developed world, however, has been adapted more slowly in the developing world. .According to iSupply, production in units of CRTs was not surpassed by LCDs production until 4Q 2007, owing largely to CRT production at factories in China.^ NATIONAL/Richardson 3" wide flat face electrostatic CRT with PDA. New, Richardson factory bulk-boxed, new production, made in Japan.
  • Sphere's Cathode Ray Tube - CRT Page 10 February 2010 13:013 UTC www.sphere.bc.ca [Source type: FILTERED WITH BAYES]

In the United Kingdom, DSG (Dixons), the largest retailer of domestic electronic equipment, reported that CRT models made up 80–90% of the volume of televisions sold at Christmas 2004 and 15–20% a year later, and that they were expected to be less than 5% at the end of 2006. Dixons ceased selling CRT televisions in 2007.[35]

Causes

.CRTs, despite recent advances, have remained relatively heavy and bulky and take up a lot of space in comparison to other display technologies, and this became a significant disadvantage as consumers considered the thin and wall-mountable flat panels a selling point.^ Organic LCD TV's (OLCD) are Introduced and promises to revolutionize flat panel displays with their thin size.

.CRT screens have much deeper cabinets compared to flat panels and rear-projection displays for a given screen size, and so it becomes impractical to have CRTs larger than 40 inches (102 cm).^ This gain, incidentally, is much larger than can be obtained from an output triode.
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^ For a transistor, the collector resistance is assumed much larger than the load resistance, so the input impedance is just the reciprocal of the transconductance.
  • Electronics 27 10 February 2010 13:013 UTC www.du.edu [Source type: FILTERED WITH BAYES]

^ CATHODE RAY TUBE (CRT) - A display device in which controlled electron beams are used to present alphanumeric or graphical data on an electroluminescent screen.

.Generally, rear-projection displays and LCDs require more power per display area than CRTs for displays larger than 12", assuming the same per sq.^ It should be noted that the total power drain of this circuit is no more than 83 mW, of which most is the filament power.
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^ In addition to the other requirements of this section, mobile and portable fluoroscopes shall provide an image receptor incorporating more than a simple fluorescent screen.
  • Electronic Code of Federal Regulations: 10 February 2010 13:013 UTC ecfr.gpoaccess.gov [Source type: Reference]

^ Failure of any single component of the cabinet x-ray system shall not cause failure of more than one required safety interlock.
  • Electronic Code of Federal Regulations: 10 February 2010 13:013 UTC ecfr.gpoaccess.gov [Source type: Reference]

cm brightness and a modern aperture grill design. .Monochrome CRTs are even more efficient than color CRTs.^ The 0Z4-G is well worth obtaining, even if it does cost more than the more common metal tube.
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^ Superconducting generators could be used to produce electrical power more efficiently than conventional generators.

^ More than 75% of TV-equipped homes are able to receive color on one or more sets.

This is because up to 2/3rds of the backlight power of LCD and rear-projection displays are lost to the RGB stripe filter. Most LCDs also have poorer color rendition and can change color with viewing angle, though modern PVA and IPS LCDs have greatly attenuated these problems. .Smaller LCD displays may be more efficient than CRT due to overhead of cathode heaters.^ Rectifier diodes often have filamentary oxide-coated cathodes, since these cathodes are more efficient when large currents are needed, requiring less power.
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^ CATHODE RAY TUBE (CRT) - A display device in which controlled electron beams are used to present alphanumeric or graphical data on an electroluminescent screen.

^ Superconducting generators could be used to produce electrical power more efficiently than conventional generators.

[citation needed]

Resurgence in specialized markets

.In the first quarter of 2008, CRTs retook the #2 technology position in North America from plasma, due to the decline and consolidation of plasma display manufacturers.^ Fluoroscopic equipment manufactured on or after June 10, 2006, shall display at the fluoroscopist's working position the AKR and cumulative air kerma.
  • Electronic Code of Federal Regulations: 10 February 2010 13:013 UTC ecfr.gpoaccess.gov [Source type: Reference]

DisplaySearch has reported that although in the 4Q of 2007 LCDs surpassed CRTs in worldwide sales, CRTs then outsold LCDs in the 1Q of 2008.[36][37]
.CRTs can be useful for displaying photos with high pixels per unit area and correct color balance.^ Toshiba 5" Circular Flat Electrostatic CRT, used in Bell and Howell and other lower frequency scopes, P31 high intensity phosphor.
  • Sphere's Cathode Ray Tube - CRT Page 10 February 2010 13:013 UTC www.sphere.bc.ca [Source type: FILTERED WITH BAYES]

^ CATHODE RAY TUBE (CRT) - A display device in which controlled electron beams are used to present alphanumeric or graphical data on an electroluminescent screen.

.LCDs, as currently the most common flatscreen technology, have generally inferior color rendition (despite having greater overall brightness) due to the fluorescent lights commonly used as a backlight.^ As most commonly used, the interelectrode transconductance between the control grid and the plate.
  • Vacuum Tube Technology: A Perspective Circa 1950 10 February 2010 13:013 UTC www.pentodepress.com [Source type: Reference]

^ Today, silicon is the most commonly used semiconductor material in the world.

[38]
.CRTs are still popular in the printing and broadcasting industries as well as in the professional video, photography, and graphics fields due to their greater color fidelity, contrast and better viewing from off-axis (wider viewing angle).^ Magnetic fields are used to deflect the electron beam in this CRT, since the magnetic fields allow for a wider-angle beam than would be possible with electric fields from charged plates.

CRTs also still find adherents in video gaming because of their higher resolution per initial cost, fast response time, and multiple native resolutions.[39]

Health concerns

Related terms:
Electronic waste

Ionizing radiation

.CRTs can emit a small amount of X-ray radiation as a result of the electron beam's bombardment of the shadow mask/aperture grille and phosphors.^ Magnetic fields are used to deflect the electron beam in this CRT, since the magnetic fields allow for a wider-angle beam than would be possible with electric fields from charged plates.

^ The electrons are liberated at the cathode by heat--thermionic emission--or as a result of bombardment by positive ions, which can cause emission of electrons or even heat the cathode the required amount for thermionic emission.
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^ Don't confuse it with the cathode-ray tube that uses a guided electron beam for oscilloscopes and TV receivers.
  • Electronics 27 10 February 2010 13:013 UTC www.du.edu [Source type: FILTERED WITH BAYES]

The amount of radiation escaping the front of the monitor is widely considered unharmful. .The Food and Drug Administration regulations in 21 C.F.R. 1020.10 are used to strictly limit, for instance, television receivers to 0.5 milliroentgens per hour (mR/h) (0.13 µC/(kg·h) or 36 pA/kg) at a distance of 5 cm (2 in) from any external surface; since 2007, most CRTs have emissions that fall well below this limit.^ Section Contents § 1020.10 Television receivers.
  • Electronic Code of Federal Regulations: 10 February 2010 13:013 UTC ecfr.gpoaccess.gov [Source type: Reference]

^ For systems that allow high voltage to be applied to the x-ray tube continuously and that control the emission of x-ray with a shutter, the radiation emitted may not exceed 0.88 milligray (vice 100 milliroentgen exposure) in 1 hour at any point 5 cm outside the external surface of the housing of the scanning mechanism when the shutter is closed.
  • Electronic Code of Federal Regulations: 10 February 2010 13:013 UTC ecfr.gpoaccess.gov [Source type: Reference]

^ Radiation exposure rates produced by a television receiver shall not exceed 0.5 milliroentgens per hour at a distance of five (5) centimeters from any point on the external surface of the receiver, as measured in accordance with this section.
  • Electronic Code of Federal Regulations: 10 February 2010 13:013 UTC ecfr.gpoaccess.gov [Source type: Reference]

[40]

Toxicity

Older color CRTs may contain toxic phosphors used for production of red. .The rear glass tube of modern CRTs may be made from leaded glass, which represent an environmental hazard if disposed of improperly.^ If it is necessary to determine such HVL at an x-ray tube potential which is not listed in table 1 in paragraph (m)(1) of this section, linear interpolation or extrapolation may be made.
  • Electronic Code of Federal Regulations: 10 February 2010 13:013 UTC ecfr.gpoaccess.gov [Source type: Reference]

^ GENERAL TUBE DATA that may interest you: CLICK HERE for General electrostatic CRT tube data (from 1955 ARRL Handbook) (browser BACK to return) .
  • Sphere's Cathode Ray Tube - CRT Page - Alphabetic prefix part numbers 10 February 2010 13:013 UTC www.sphere.bc.ca [Source type: FILTERED WITH BAYES]

^ Originally, tubes had bases (usually Bakelite) to support the contact pins mechanically, taking the strain off the pressed-glass seal, which was made of lead glass.
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[41] .By the time personal computers were produced, glass in the front panel (the viewable portion of the CRT) used barium rather than lead, though the rear of the CRT was still produced from leaded glass.^ Magnetic fields are used to deflect the electron beam in this CRT, since the magnetic fields allow for a wider-angle beam than would be possible with electric fields from charged plates.

^ The electron microscope uses a beam of electrons rather than light to study objects too small for conventional light microscopes.

^ They can thus be used instead of transistors in computers to produce machines that operate many times faster than present day machines and that are much smaller, since no space needs to left inside such machines for heat dissipation purposes.

Monochrome CRTs typically do not contain enough leaded glass to fail EPA tests.
In October 2001, the United States Environmental Protection Agency created rules stating that CRTs must be brought to special recycling facilities. In November 2002, the EPA began fining companies that disposed of CRTs through landfills or incineration. Regulatory agencies, local and statewide, monitor the disposal of CRTs and other computer equipment.[42]
In Europe, disposal of CRT televisions and monitors is covered by the WEEE Directive.[43]

Flicker

.At low refresh rates (below 60 Hz), the periodic scanning of the display may produce an irritating flicker that some people perceive more easily than others, especially when viewed with peripheral vision.^ In addition to the other requirements of this section, mobile and portable fluoroscopes shall provide an image receptor incorporating more than a simple fluorescent screen.
  • Electronic Code of Federal Regulations: 10 February 2010 13:013 UTC ecfr.gpoaccess.gov [Source type: Reference]

^ This amplifier makes a good construction project if you would like to have a small vacuum-tube amplifier at low cost, no more than $35 or so.
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^ C is selected so the -3dB point of the RC filter is at the desired low frequency f o = 1/2πRC. In the present case, with f o = 60 Hz, C = 0.0056 μF. Therefore, C = 0.033 is ample.
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A high refresh rate (above 72 Hz) reduces the effect. .Computer displays and televisions with CRTs driven by digital electronics often use refresh rates of 100 Hz or more to largely eliminate any perception of flicker.^ They are used worldwide in a huge range of electronics applications computers, medical equipment, telecommunications, industrial equipment, household devices such as stereos and so on.

^ Magnetic fields are used to deflect the electron beam in this CRT, since the magnetic fields allow for a wider-angle beam than would be possible with electric fields from charged plates.

^ CATHODE RAY TUBE (CRT) - A display device in which controlled electron beams are used to present alphanumeric or graphical data on an electroluminescent screen.

[44] .Non-computer CRTs or CRT for sonar or radar may have long persistence phosphor and are thus flicker free.^ All CRT's have been tested for a good filament , and have burn-free phosphors.
  • Sphere's Cathode Ray Tube - CRT Page 10 February 2010 13:013 UTC www.sphere.bc.ca [Source type: FILTERED WITH BAYES]

If the persistence is too long on a video display, moving images will be blurred.

High-frequency noise

.CRTs used for television operate with a horizontal scanning frequencies of 15,734 Hz (for NTSC systems) or 15,625 Hz (for PAL systems).^ COMMUNICATION DECEPTION - (1) Use of devices, operations, and techniques with the intent of confusing or misleading the user of a communications link or a navigation system.

^ To produce television images in Australia, the image formed by the optical lens system of the camera is scanned electronically as a sequence of 625 vertically displaced horizontal lines.

^ Such lasers also can be made to scan through a range of output of colors, or even frequency hop , using a piezo-driven grating.

[45] .These frequencies are at the upper range of human hearing and are inaudible to many people; some people will perceive a high-pitched tone near an operating television CRT.[46] The sound is due to magnetostriction in the magnetic core of the flyback transformer.^ CRYSTAL VIDEO RECEIVER - A simple and inexpensive SIGINT receiver offering a high probability of intercept (POI) within its frequency range.

^ These rectifiers took the high frequency alternating signal of the radio wave and extracted the low frequencies necessary for the headphones.

^ Since we are already 3 dB down at 450 kHz, some other factor is spoiling the high-frequency end of the passband.
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Implosion

.A high vacuum exists within all cathode ray tubes.^ The following diagram shows a cathode ray tube with the various glows and dark spaces labelled.

^ These rays were eventually named cathode rays , as they appeared to come from the cathode (negative electrode) of the tube.

^ X-ray high-voltage generator means a device which transforms electrical energy from the potential supplied by the x-ray control to the tube operating potential.
  • Electronic Code of Federal Regulations: 10 February 2010 13:013 UTC ecfr.gpoaccess.gov [Source type: Reference]

If the outer glass envelope is damaged, a dangerous implosion may occur. Glass pieces may explode outwards at dangerous velocities. .While modern CRTs used in televisions and computer displays have epoxy-bonded face-plates or other measures to prevent shattering of the envelope, CRTs removed from equipment must be handled carefully to avoid personal injury.^ Magnetic fields are used to deflect the electron beam in this CRT, since the magnetic fields allow for a wider-angle beam than would be possible with electric fields from charged plates.

^ CATHODE RAY TUBE (CRT) - A display device in which controlled electron beams are used to present alphanumeric or graphical data on an electroluminescent screen.

^ Note very carefully that one side of the supply is connected to the AC line, and this must be the grounded side, for your safety, and to avoid ground loops.
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[47]

Security concerns

.Under some circumstances, the signal radiated from the electron guns, scanning circuitry, and associated wiring of a CRT can be captured and used to remotely reconstruct what is shown on the CRT, using a process called Van Eck phreaking.^ The brightness of the image on the screen is controlled by the signal voltages applied to the grid in the electron gun of the picture tube.

^ A signal generating electron-beam tube in which a picture signal is produced by scanning an electrode, parts of which have different secondary-emission characteristics.
  • Vacuum Tube Technology: A Perspective Circa 1950 10 February 2010 13:013 UTC www.pentodepress.com [Source type: Reference]

^ Detectors collect the backscattered and secondary electrons coming from the surface and convert them into a signal that in turn is used to produce an image of the sample.

[48] Special TEMPEST shielding can mitigate this effect. .Such radiation of a potentially exploitable signal however occurs also with LCDs and with all electronics in general.^ If an alternating potential difference is applied across a diode a current only occurs when the potential difference is such that the anode is positive with respect to the cathode.

^ The name "receiving" comes from their use in radio receivers, their principal commercial application, but refers to all small vacuum tubes for general electronic purposes.
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^ CYCLOSTATIONARITY - A statistical property exhibited by essentially all digital signals and some naturally occurring waveforms.

See also

References

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Selected patents

External links


Simple English

File:Cathode ray
Cathode ray tube using electromagnetic focus and deflection

The cathode ray tube or CRT was invented by Karl Ferdinand Braun. It is the display device that was used in most computer monitors and televisions before LCD and plasma screens started being used.

A cathode ray tube is an electron gun. It is a vacuumed glass container with a cathode (an electrode with negative charge) at one end. The heater is like a light bulb. It heats up and gives out electrons. The cathode repels the electrons towards the screen because they have the same charge. The anodes attract and speed the electrons up because they have the opposite charge.

When these electrons hit the phosphor screen, they cause that small part of the screen to light up. The 4 plates move the electrons up, down, left and right onto a spot on the screen.

CRTs can also be used as particle accelerators.

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Up to date as of December 28, 2010

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