Neon lamp
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A neon lamp (also neon glow lamp) is a miniature
gas discharge lamp Gas-discharge lamps are a family of artificial light sources that generate light by sending an electric discharge through an ionized gas, a plasma. Typically, such lamps use a noble gas (argon, neon, krypton, and xenon) or a mixture of these ...
. The lamp typically consists of a small glass capsule that contains a mixture of
neon Neon is a chemical element with the symbol Ne and atomic number 10. It is a noble gas. Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air. It was discovered (along with krypton ...
and other gases at a low pressure and two
electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...
s (an
anode An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic is ...
and a
cathode A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in whi ...
). When sufficient voltage is applied and sufficient current is supplied between the electrodes, the lamp produces an orange
glow discharge A glow discharge is a plasma formed by the passage of electric current through a gas. It is often created by applying a voltage between two electrodes in a glass tube containing a low-pressure gas. When the voltage exceeds a value called the str ...
. The glowing portion in the lamp is a thin region near the cathode; the larger and much longer
neon sign In the signage industry, neon signs are electric signs lighted by long luminous gas-discharge tubes that contain rarefied neon or other gases. They are the most common use for neon lighting, which was first demonstrated in a modern form in Decem ...
s are also glow discharges, but they use the positive column which is not present in the ordinary neon lamp. Neon glow lamps were widely used as
indicator lamp A check engine light or malfunction indicator lamp (MIL), is a tell-tale that a computerized engine-management system uses to indicate a malfunction. Found on the instrument panel of most automobiles, it usually bears the legend , , , , , o ...
s in the displays of electronic instruments and appliances. They are still sometimes used for their electrical simplicity in high-voltage circuits.


History

Neon Neon is a chemical element with the symbol Ne and atomic number 10. It is a noble gas. Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air. It was discovered (along with krypton ...
was discovered in 1898 by
William Ramsay Sir William Ramsay (; 2 October 1852 – 23 July 1916) was a Scottish chemist who discovered the noble gases and received the Nobel Prize in Chemistry in 1904 "in recognition of his services in the discovery of the inert gaseous elements ...
and Morris W. Travers. The characteristic, brilliant red color that is emitted by gaseous neon when excited electrically was noted immediately; Travers later wrote, "the blaze of crimson light from the tube told its own story and was a sight to dwell upon and never forget." Neon's scarcity precluded its prompt application for electrical lighting along the lines of
Moore tube Daniel McFarlan Moore (February 27, 1869 – June 15, 1936) was a U.S. electrical engineer and inventor. He developed a novel light source, the "Moore lamp", and a business that produced them in the early 1900s. The Moore lamp was the first co ...
s, which used electric discharges in nitrogen. Moore tubes were commercialized by their inventor,
Daniel McFarlan Moore Daniel McFarlan Moore (February 27, 1869 – June 15, 1936) was a U.S. electrical engineer and inventor. He developed a novel light source, the "Moore lamp", and a business that produced them in the early 1900s. The Moore lamp was the first co ...
, in the early 1900s. After 1902,
Georges Claude Georges Claude (24 September 187023 May 1960) was a French engineer and inventor. He is noted for his early work on the industrial liquefaction of air, for the invention and commercialization of neon lighting, and for a large experiment on genera ...
's company,
Air Liquide Air Liquide S.A. (; ; literally "liquid air"), is a French multinational company which supplies industrial gases and services to various industries including medical, chemical and electronic manufacturers. Founded in 1902, after Linde it is ...
, was producing industrial quantities of neon as a byproduct of his air liquefaction business, and in December 1910 Claude demonstrated modern
neon light Neon lighting consists of brightly glowing, electrified glass tubes or bulbs that contain rarefied neon or other gases. Neon lights are a type of cold cathode gas-discharge light. A neon tube is a sealed glass tube with a metal electrode a ...
ing based on a sealed tube of neon. In 1915 a U.S. patent was issued to Claude covering the design of the electrodes for neon tube lights; this patent became the basis for the monopoly held in the U.S. by his company, Claude Neon Lights, through the early 1930s. Around 1917, Daniel Moore developed the neon lamp while working at the
General Electric Company The General Electric Company (GEC) was a major British industrial conglomerate involved in consumer and defence electronics, communications, and engineering. The company was founded in 1886, was Britain's largest private employer with over 250 ...
. The lamp has a very different design from the much larger neon tubes used for
neon lighting Neon lighting consists of brightly glowing, electrified glass tubes or bulbs that contain rarefied neon or other gases. Neon lights are a type of cold cathode gas-discharge light. A neon tube is a sealed glass tube with a metal electrode ...
. The difference in design was sufficient that a U.S. patent was issued for the lamp in 1919. A Smithsonian Institution website notes, "These small, low power devices use a physical principle called
coronal discharge A corona discharge is an electrical discharge caused by the ionization of a fluid such as air surrounding a conductor carrying a high voltage. It represents a local region where the air (or other fluid) has undergone electrical breakdown ...
. Moore mounted two electrodes close together in a bulb and added neon or argon gas. The electrodes would glow brightly in red or blue, depending on the gas, and the lamps lasted for years. Since the electrodes could take almost any shape imaginable, a popular application has been fanciful decorative lamps. Glow lamps found practical use as indicators in instrument panels and in many home appliances until the widespread commercialization of
light-emitting diode A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...
s (LEDs) in the 1970s.


Description

A small
electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...
(for a 5 mm bulb diameter NE-2 lamp, the
quiescent current In electronics, biasing is the setting of DC (direct current) operating conditions (current and voltage) of an active device in an amplifier. Many electronic devices, such as diodes, transistors and vacuum tubes, whose function is processing ...
is about 400 µA), which may be AC or DC, is allowed through the tube, causing it to glow orange-red. The gas is typically a
Penning mixture A Penning mixture, named after Frans Michel Penning, is a mixture of gases used in electric lighting or displaying fixtures. Although the popular phrase for the most common of these is a neon lamp, it is more efficient to have the glass tube fille ...
, 99.5%
neon Neon is a chemical element with the symbol Ne and atomic number 10. It is a noble gas. Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air. It was discovered (along with krypton ...
and 0.5%
argon Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abu ...
, which has lower
striking voltage The breakdown voltage of an insulator is the minimum voltage that causes a portion of an insulator to experience electrical breakdown and become electrically conductive. For diodes, the breakdown voltage is the minimum reverse voltage that make ...
than pure neon, at a pressure of . The lamp
glow discharge A glow discharge is a plasma formed by the passage of electric current through a gas. It is often created by applying a voltage between two electrodes in a glass tube containing a low-pressure gas. When the voltage exceeds a value called the str ...
lights at its striking voltage. The striking voltage is reduced by ambient light or radioactivity. To reduce the "dark effect", some lamps were made with a small amount of radioactive material, typically
Krypton-85 Krypton-85 (85Kr) is a radioisotope of krypton. Krypton-85 has a half-life of 10.756 years and a maximum decay energy of 687 keV. It decays into stable rubidium-85. Its most common decay (99.57%) is by beta particle emission with maximum energy ...
, added to the envelope to provide ionization in darkness. The voltage required to sustain the discharge is significantly (up to 30%) lower than the striking voltage. This is due to the organization of positive ions near the cathode. Neon lamps operate using a low current
glow discharge A glow discharge is a plasma formed by the passage of electric current through a gas. It is often created by applying a voltage between two electrodes in a glass tube containing a low-pressure gas. When the voltage exceeds a value called the str ...
. Higher power devices, such as
mercury-vapor lamp A mercury-vapor lamp is a gas-discharge lamp that uses an electric arc through vaporized mercury to produce light. The arc discharge is generally confined to a small fused quartz arc tube mounted within a larger soda lime or borosilicate glass ...
s or
metal halide lamp A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
s use a higher current
arc discharge An electric arc, or arc discharge, is an electrical breakdown of a gas that produces a prolonged electrical discharge. The electric current, current through a normally Electrical conductance, nonconductive medium such as air produces a plasma (p ...
. Low pressure
sodium-vapor lamp A sodium-vapor lamp is a gas-discharge lamp that uses sodium in an excited state to produce light at a characteristic wavelength near 589  nm. Two varieties of such lamps exist: low pressure and high pressure. Low-pressure sodium lamps are ...
s use a neon Penning mixture for warm up and can be operated as giant neon lamps if operated in a low power mode.


Limiting current

Once the neon lamp has reached breakdown, it can support a large current flow. Because of this characteristic, electrical circuitry external to the neon lamp must limit the current through the circuit or else the current will rapidly increase until the lamp is destroyed. For indicator-sized lamps, a
resistor A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active el ...
typically limits the current. In contrast, larger sized lamps often use a specially constructed high voltage
transformer A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...
with high
leakage inductance Leakage inductance derives from the electrical property of an imperfectly-coupled transformer whereby each winding behaves as a self-inductance in series with the winding's respective ohmic resistance constant. These four winding constants also in ...
or other
electrical ballast An electrical ballast is a device placed in series with a load to limit the amount of electric current, current in an electrical network, electrical circuit. A familiar and widely used example is the inductive ballast used in fluorescent lamp ...
to limit the available current (see
neon sign In the signage industry, neon signs are electric signs lighted by long luminous gas-discharge tubes that contain rarefied neon or other gases. They are the most common use for neon lighting, which was first demonstrated in a modern form in Decem ...
).


Flicker flame

When the current through the lamp is lower than the current for the highest-current discharge path, the
glow discharge A glow discharge is a plasma formed by the passage of electric current through a gas. It is often created by applying a voltage between two electrodes in a glass tube containing a low-pressure gas. When the voltage exceeds a value called the str ...
may become unstable and not cover the entire surface of the electrodes. This may be a sign of aging of the indicator lamp, and is exploited in the decorative "flicker flame" neon lamps. However, while too low a current causes flickering, too high a current increases the wear of the electrodes by stimulating
sputtering In physics, sputtering is a phenomenon in which microscopic particles of a solid material are ejected from its surface, after the material is itself bombarded by energetic particles of a plasma or gas. It occurs naturally in outer space, and can ...
, which coats the internal surface of the lamp with metal and causes it to darken. The potential needed to strike the discharge is higher than what is needed to sustain the discharge. When there is not enough current, the glow forms around only part of the electrode surface. Convective currents make the glowing areas flow upwards, not unlike the discharge in a
Jacob's ladder Jacob's Ladder ( he, סֻלָּם יַעֲקֹב ) is a ladder leading to heaven that was featured in a dream the biblical Patriarch Jacob had during his flight from his brother Esau in the Book of Genesis (chapter 28). The significance of th ...
. A
photoionization Photoionization is the physical process in which an ion is formed from the interaction of a photon with an atom or molecule. Cross section Not every interaction between a photon and an atom, or molecule, will result in photoionization. The prob ...
effect can also be observed here, as the electrode area covered by the glow discharge can be increased by shining light at the lamp.


Efficiency

In comparison with
incandescent lamps An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a wire filament heated until it glows. The filament is enclosed in a glass bulb with a vacuum or inert gas to protect the filament from oxidat ...
, neon lamps have much higher
luminous efficacy Luminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power, measured in lumens per watt in the International System of Units (SI). Depending on context, the power can be either the ...
.
Incandescence Incandescence is the emission of electromagnetic radiation (including visible light) from a hot body as a result of its high temperature. The term derives from the Latin verb ''incandescere,'' to glow white. A common use of incandescence is ...
is heat-driven light emission, so a large portion of the electric energy put into an incandescent lamp is converted into heat. Non-incandescent light sources such as neon lamps,
fluorescent lamp A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet lig ...
s, and
light emitting diodes A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...
are therefore much more energy efficient than normal incandescent lamps.
Green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 Nanometre, nm. In subtractive color systems, used in painting and color printing, it is created by ...
neon lamps can produce up to 65 lumens per watt of power input, while white neon lamps have an efficacy of around 50 lumens per watt. In contrast, a standard incandescent lamp only produces around 13.5 lumens per watt.


Environmental effects

The precise values of starting and maintaining voltages of neon lamps is subject to change due to several effects. External light falling on the electrodes provides a source of ionization to start the lamp; in total darkness, lamps may reach a high and erratic starting voltage. One measure to mitigate for this effect is to include a pilot lamp within the enclosure to provide an initial source of light. Lamps are also somewhat sensitive to external electrostatic fields, temperature, and aging. Lamps intended for use as circuit components may be specially processed to eliminate most of the initial aging effects.


Applications


Visual indicator

Small neon lamps are most widely used as visual indicators in electronic equipment and appliances, due to their low power consumption, long life, and ability to operate on mains power.


Voltage surge suppression

Neon lamps are commonly used as low-voltage
surge protector A 'surge protector'' (or spike suppressor, surge suppressor, surge diverter, surge protection device (SPD) or transient voltage surge suppressor (TVSS) is an appliance or device intended to protect electrical devices from voltage spikes in alt ...
s, but they are generally inferior to gas discharge tube (GDT) surge protectors (which can be designed for higher voltage applications). Neon lamps have been used as an inexpensive method to protect RF receivers from voltage spikes (lamp connected to RF input and chassis ground), but they are not suitable for higher-power RF transmitters.


Voltage tester

Most small neon (indicator-sized) lamps, such as the common NE-2, have a break-down voltage of around 90 
volt The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827). Defi ...
s. When driven from a DC source, only the negatively charged electrode (
cathode A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in whi ...
) will glow. When driven from an AC source, both electrodes will glow (each during alternate half cycles). These attributes make neon lamps (with series resistors) a convenient low-cost voltage tester. By examining which electrode is glowing they can reveal whether a given voltage source is AC or DC, and if DC, the polarity of the points being tested.


Voltage regulation

The breakdown characteristic of glow-discharge lamps allows them to be used as
voltage regulator A voltage regulator is a system designed to automatically maintain a constant voltage. A voltage regulator may use a simple feed-forward design or may include negative feedback. It may use an electromechanical mechanism, or electronic components ...
s or
overvoltage When the voltage in a circuit or part of it is raised above its upper design limit, this is known as overvoltage. The conditions may be hazardous. Depending on its duration, the overvoltage event can be transient—a voltage spike—or perm ...
protection devices.Miller, W.G. (1969)
Using and Understanding Miniature Neon Lamps
'', p.25-35
Starting around the 1930s,
General Electric General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable energ ...
(GE), Signalite, and other firms made voltage regulator tubes.


Switching element/oscillator

Like other
gas discharge lamp Gas-discharge lamps are a family of artificial light sources that generate light by sending an electric discharge through an ionized gas, a plasma. Typically, such lamps use a noble gas (argon, neon, krypton, and xenon) or a mixture of these ...
s, the neon lamp has
negative resistance In electronics, negative resistance (NR) is a property of some electrical circuits and devices in which an increase in voltage across the device's terminals results in a decrease in electric current through it. This is in contrast to an ordi ...
; its voltage falls with increasing current after the lamp reaches its breakdown voltage. Therefore, the lamp has
hysteresis Hysteresis is the dependence of the state of a system on its history. For example, a magnet may have more than one possible magnetic moment in a given magnetic field, depending on how the field changed in the past. Plots of a single component of ...
; its turn-off (extinction) voltage is lower than its turn-on (breakdown) voltage. This allows it to be used as an active switching element. Neon lamps were used to make
relaxation oscillator In electronics a relaxation oscillator is a nonlinear electronic oscillator circuit that produces a nonsinusoidal repetitive output signal, such as a triangle wave or square wave. on Peter Millet'Tubebookswebsite The circuit consists of a feedba ...
circuits, using this mechanism, sometimes referred to as the
Pearson–Anson effect The Pearson–Anson effect, discovered in 1922 by Stephen Oswald PearsonStephen Oswald Pearson,''Dictionary of Wireless Technical Terms'' (London: Iliffe & Sons, 1926). and Horatio Saint George Anson, is the phenomenon of an oscillating electric ...
GE Glow Lamp Manual 1965
, p.14-18
for low frequency applications such as flashing warning lights,
stroboscope A stroboscope, also known as a strobe, is an instrument used to make a cyclically moving object appear to be slow-moving, or stationary. It consists of either a rotating disk with slots or holes or a lamp such as a flashtube which produces br ...
s tone generators in electronic organs, and as time bases and deflection oscillators in early
cathode ray oscilloscope An oscilloscope (informally a scope) is a type of electronic test instrument that graphically displays varying electrical voltages as a two-dimensional plot of one or more signals as a function of time. The main purposes are to display repetiti ...
s. Neon lamps can also be bistable, and were even used to build
digital logic A logic gate is an idealized or physical device implementing a Boolean function, a logical operation performed on one or more Binary number, binary inputs that produces a single binary output. Depending on the context, the term may refer to an id ...
circuits such as
logic gate A logic gate is an idealized or physical device implementing a Boolean function, a logical operation performed on one or more binary inputs that produces a single binary output. Depending on the context, the term may refer to an ideal logic gate, ...
s, flip-flop,
binary Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two digits (0 and 1) * Binary function, a function that takes two arguments * Binary operation, a mathematical operation that t ...
memories Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, ...
, and
digital counter In digital logic and computing, a counter is a device which stores (and sometimes displays) the number of times a particular event or process has occurred, often in relationship to a clock. The most common type is a sequential digital logic circ ...
s.GE Glow Lamp Manual 1965
, p.35-36, 41-66
These applications were sufficiently common that manufacturers made neon lamps specifically for this use, sometimes called "circuit-component" lamps. At least some of these lamps have a glow concentrated into a small spot on the cathode, which made them unsuited to use as indicators. To provide more repeatable lamp characteristics and reduce "dark effect" ( a rise in starting voltage observed in lamps kept in total darkness), some types of lamp such as NE83 (5AH) include a small amount of a radioisotope to provide initial ionization. A variant of the NE-2 type lamp for circuit applications, the NE-77, have three wire electrodes in the lamp (in a plane) instead of the usual two, the third for use as a control electrode.


Detector

Neon lamps have been historically used as microwave and millimeter-wave detectors ("plasma diodes" or glow discharge detectors (GDDs)) up to about 100 GHz or so and in such service were said to exhibit comparable sensitivity (of the order of a few 10s to perhaps 100 microvolts) to the familiar 1N23-type catwhisker-contacted silicon diodes once ubiquitous in microwave equipment. More recently it has been found that these lamps work well as detectors even at sub-millimeter ("terahertz") frequencies and they have been successfully used as pixels in several experimental imaging arrays at these wavelengths. In these applications the lamps are operated either in "starvation" mode (to reduce lamp-current noise) or in normal glow discharge mode; some literature references their use as detectors of radiation up into the optical regime when operated in abnormal glow mode. Coupling of microwaves into the plasma may be in free space, in waveguide, by means of a parabolic concentrator (e.g.,
Winston cone A Winston cone is a non-imaging light collector in the shape of an Parabolic_reflector#Off-axis_reflectors, off-axis parabola of revolution with a reflective inner surface. It concentrates the light passing through a relatively large entrance apertu ...
), or via capacitive means via a loop or dipole antenna mounted directly to the lamp. Although most of these applications use ordinary off-the-shelf dual-electrode lamps, in one case it was found that special three (or more) electrode lamps, with the extra electrode acting as the coupling antenna, provided even better results (lower noise and higher sensitivity). This discovery received a US patent.


Alphanumerical display

Neon lamps with several shaped electrodes were used as alphanumerical displays known as
Nixie tube A Nixie tube ( ), or cold cathode display, is an electronic device used for displaying numerals or other information using glow discharge. The glass tube contains a wire-mesh anode and multiple cathodes, shaped like numerals or other symbols ...
s. These have since been replaced by other display devices such as
light emitting diode A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...
s,
vacuum fluorescent display A vacuum fluorescent display (VFD) is a display device once commonly used on consumer electronics equipment such as video cassette recorders, car radios, and microwave ovens. A VFD operates on the principle of cathodoluminescence, roughly s ...
s, and
liquid crystal display A liquid-crystal display (LCD) is a flat panel display, flat-panel display or other Electro-optic modulator, electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liqui ...
s. Since at least the 1940s, argon, neon, and
phosphor A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or vi ...
ed ''glow
thyratron A thyratron is a type of gas-filled tube used as a high-power electrical switch and controlled rectifier. Thyratrons can handle much greater currents than similar hard-vacuum tubes. Electron multiplication occurs when the gas becomes ionized, pro ...
'' latching indicators (which would light up upon an impulse on their starter electrode and extinguish only after their anode voltage was cut) were available for example as self-displaying
shift registers A shift register is a type of digital circuit using a cascade of flip-flops where the output of one flip-flop is connected to the input of the next. They share a single clock signal, which causes the data stored in the system to shift from one lo ...
in large-format, crawling-text
dot-matrix display A dot-matrix display is a low cost electronic digital display device that displays information on machines such as clocks, watches, calculators, and many other devices requiring a simple alphanumeric (and/or graphic) display device of limited re ...
s, or, combined in a 4×4, four-color phosphored-thyratron matrix, as a stackable 625-color RGBA pixel for large video graphics arrays. Multiple-cathode and/or anode ''glow thyratrons'' called
Dekatron In electronics, a Dekatron (or Decatron, or generically three-phase gas counting tube or glow-transfer counting tube or cold cathode tube) is a gas-filled decade counting tube. Dekatrons were used in computers, calculators, and other counti ...
s could count forwards and backwards while their count state was visible as a glow on one of the numbered cathodes. These were used as self-displaying divide-by-n counter/timer/prescalers in counting instruments, or as adder/subtracters in
calculators An electronic calculator is typically a portable electronic device used to perform calculations, ranging from basic arithmetic to complex mathematics. The first solid-state electronic calculator was created in the early 1960s. Pocket-size ...
.


Other

In 1930s radio sets, neon lamps were used as tuning indicators, called "tuneons" and would give a brighter glow as the station was tuned in correctly. Because of their comparatively short response time, in the early development of
television Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of television transmission. Television is a mass medium for advertisin ...
neon lamps were used as the light source in many mechanical-scan TV displays. Novelty glow lamps with shaped electrodes (such as flowers and leaves), often coated with phosphors, have been made for artistic purposes. In some of these, the glow that surrounds an electrode is part of the design.


Color

Neon indicator lamps are normally orange, and are frequently used with a colored filter over them to improve contrast and change their color to red or a redder orange. They can also be filled with
argon Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abu ...
,
krypton Krypton (from grc, κρυπτός, translit=kryptos 'the hidden one') is a chemical element with the symbol Kr and atomic number 36. It is a colorless, odorless, tasteless noble gas that occurs in trace amounts in the atmosphere and is often ...
, or
xenon Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...
rather than neon, or mixed with it. While the electrical operating characteristics remain similar, these lamps light with a bluish glow (including some
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
) rather than neon's characteristic reddish-orange glow. Ultraviolet radiation then can be used to excite a
phosphor A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or vi ...
coating inside of the bulb and provide a wide range of various colors, including white. A mixture of 95% neon, 2.5%
krypton Krypton (from grc, κρυπτός, translit=kryptos 'the hidden one') is a chemical element with the symbol Kr and atomic number 36. It is a colorless, odorless, tasteless noble gas that occurs in trace amounts in the atmosphere and is often ...
, and 2.5% argon can be used for a green glow, but nevertheless "green neon" lamps are more commonly phosphor-based.


See also

* Aerolux Light Corporation *
Gas-filled tube A gas-filled tube, also commonly known as a discharge tube or formerly as a Plücker tube, is an arrangement of electrodes in a gas within an insulating, temperature-resistant envelope. Gas-filled tubes exploit phenomena related to electric d ...
*
Light art Light art or The Art of Light is generally referring to a visual art form in which (physical) light is the main, if not sole medium of creation. Uses of the term differ drastically in incongruence; definitions, if existing, vary in several asp ...
*
List of light sources This is a list of sources of light, the visible part of the electromagnetic spectrum. Light sources produce photons from another energy source, such as heat, chemical reactions, or conversion of mass or a different frequency of electromagnetic ener ...
*
Magic eye tube A magic eye tube or tuning indicator, in technical literature called an electron-ray indicator tube, is a vacuum tube which gives a visual indication of the amplitude of an electronic signal, such as an audio output, radio-frequency signal stren ...
*
Neon sign In the signage industry, neon signs are electric signs lighted by long luminous gas-discharge tubes that contain rarefied neon or other gases. They are the most common use for neon lighting, which was first demonstrated in a modern form in Decem ...
* Pearson-Anson effect * Timeline of lighting technology


References


Further reading

* ''Using and Understanding Miniature Neon Lamps''; 1st Ed; William G. Miller; Sams Publishing; 127 pages; 1969; LCCN 69-16778
''(archive)''
* ''Cold Cathode Tubes''; 1st Ed; J.B. Dance; Iliffe Books; 125 pages; 1967
''(archive)''
* ''Glow Lamp Manual - Theory, Circuits, Ratings''; 2nd Ed; General Electric; 122 pages; 1966
''(archive)''
* ''Applications of Neon Lamps and Gas Discharge Tubes''; 1st Ed; Edward Bauman; Carlton Press; 1966
''(archive)''


External links



- Clifton Laboratories
Neon Indicator Lamp Datasheet
- VCC (Visual Communications Company) parent of Chicago Miniature Lighting (CML) {{Authority control Products introduced in 1902 Types of lamp Neon lighting Vacuum tube displays