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About glow lamps
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Was it a question of what neon lamps
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Areas of application of glow lamps
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Designs of glow lamps
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Our practical tips
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Useful life information
Was it a question of what neon lamps
Figure: Glow lamp with glass piston and plate electrodes for signal display
A glow lamp is an electrical component that emits a faint glow – a glow – when an electrical voltage is applied. Physically, the formation of the glow light is based on the principle of gas discharge.
To do this, a bulb piston, in d.
This effect is used, for example, for overvoltage protection. In order to keep the "avalanche" – and thus the current – in check, glow lamps are usually used for signal purposes with defined series resistors for current limitation.In order to keep the two electrodes in check, they are filled with a noble gas. The gas has a low overpressure and the ends of the electrodes within the lamp are very close to each other. If voltage is applied to the electrodes, so-called shock ionization in the inert gas develops due to the electrical fields surrounding the electrodes. Escaping electrons collide with particles of the inert gas, was ionized and stimulated to glow – the glow is formed. Once this process is started, further particles are triggered and ionized, was this results in an avalanche effect. More and more conductive particles are in the glowing cloud. As a result, the current flowing through the system increases very quickly.
The indicated lighting effect is always only present at the negative electrode. In the case of alternating voltage, the two electrodes of a glow lamp light up alternately. The human eye cannot distinguish between 50 Hertz changes, so that a phase tester appears to light up on both electrodes of the glow lamp.
The color of the glow discharge depends on the inert gas used. When neon is used, reddish-orange glimming is produced. The ignition voltage of a glow lamp depends on the gas used, the distance between the electrodes and the internal pressure in the lamp.
The common range is 50 to 150 volts ignition voltage and 40 to 90 volts burning voltage. Compared to incandescent lamps, the glow lamp performs much better with regard to the light yield, calculated on the basis of the energy used.
By the way: In English, the term "neon lamp" is used for neon lamps, even if no neon is used.
Areas of application of glow lamps
Glow lamps are used in many electrical devices as signal lamps, if the actual device does not require a lower internal operating voltage, but is operated directly with the mains voltage. The direct connection of a glow lamp with series resistor saves the time-consuming provision of low voltage for signal LEDs via power supply. These directly operated 230 volt devices include irons or conventional filter coffee machines. Glow lamps can also be found in the illuminated switches of sockets or socket strips and distributors for signaling the on/off state.
In addition, glow lamps are used in switch programs of some manufacturers, such as Gira and others, and serve here to display switching states. It is also easier to find switches and sockets in the dark, thanks to the bulbs, for example in the case of push buttons in the house floor lighting or sockets in darkened laboratories. A well-known application is not least the phase tester, and glow lamps are also widely used in modeling.
Two other areas of application should not be forgotten: Firstly, the function of the glow lamp as a switch. It is used, for example, to start conventional fluorescent tubes with ballast. On the other hand, the glow lamp can generate electrical vibrations for simple vibration circuits due to its physical characteristic curve. This effect, known from physics, was used among other things in the first electronic musical instruments.
Designs of glow lamps
Mini neon lamps with wire ends without series resistor and base.
Wire ends are used for soldering or fixing in terminals (see figure on the left) for installing glow lamps.
But threads in sizes E10 and E14 are also common (see figure 1 above).
The required series resistor for current limitation is usually integrated. There are also glow lamps with plug-in contacts for special sockets or with bayonet sockets.
If the lamp itself is visible, smooth bulb bulbs are the first choice.
Our practical tips:
Change of glow lamps
Neon lamps with plug or screw sockets are small and often placed in places that are difficult to access. So-called lamp cutters are available for the replacement of these lamps, which are available in the diameters of the lamp bulbs.
Phase tester with glow lamp
A phase tester with glow lamp is only a single-pole voltage tester and thus a purely qualitative measuring medium. The luminous intensity does not tell anything about the voltage level or current, but only signals whether the phase, i.e. the external conductor P, is present at the tested conductor in the low-voltage network. Further statements only allow two-pole voltage testers.
Useful life information
Despite the winning train of the LED, the glow lamp is still very popular, because it can score points with low production and operating costs, among other things. Depending on the operating current, they can reach a service life of up to 100,000 hours, which was equivalent to continuous operation of more than 11 years. When used exclusively with direct current, the service life of the lamp is reduced by around 40 percent compared to AC operation due to the one-sided wear of only one electrode of the lamp.