Nixie tube
The tube is filled with a gas at low pressure, usually mostly neon and a small amount of argon, in a Penning mixture.
[2][3] In later nixies, in order to extend the usable life of the device, a tiny amount of mercury was added to reduce cathode poisoning and sputtering.
Although it resembles a vacuum tube in appearance, its operation does not depend on thermionic emission of electrons from a hot cathode.
The magnetic field and voltages applied to the electrodes made the electrons form a thick sheet (as in a cavity magnetron) that went to only one anode.
Glow-transfer counting tubes, similar in essential function to the trochotrons, had a glow discharge on one of a number of main cathodes, visible through the top of the glass envelope.
There were a number of relevant patents filed by Northrop and others around the early 1950s, and the first mass-produced display tubes were introduced in 1954 by National Union Co. under the brand name Inditron.
The most common form of Nixie tube has ten cathodes in the shapes of the numerals 0 to 9 (and occasionally a decimal point or two), but there are also types that show various letters, signs and symbols.
Longer-life tubes that were manufactured later in the Nixie timeline have mercury added to reduce sputtering[4] resulting in a blue or purple tinge to the emitted light.
Nixies were used as numeric displays in early digital voltmeters, multimeters, frequency counters and many other types of technical equipment.
Cathode poisoning can be abated by limiting current through the tubes to significantly below their maximum rating,[12] through the use of Nixie tubes constructed from materials that avoid the effect (e.g. by being free of silicates and aluminum), or by programming devices to periodically cycle through all digits so that seldom-displayed ones get activated.
[13] As testament to their longevity, and that of the equipment which incorporated them, as of 2006[update] several suppliers still provided common Nixie tube types as replacement parts, new in original packaging.
Before Nixie tubes became prominent, most numeric displays were electromechanical, using stepping mechanisms to display digits either directly by use of cylinders bearing printed numerals attached to their rotors, or indirectly by wiring the outputs of stepping switches to indicator bulbs.
The VFD uses a hot filament to emit electrons, a control grid and phosphor-coated anodes (similar to a cathode-ray tube) shaped to represent segments of a digit, pixels of a graphical display, or complete letters, symbols, or words.
Unlike Nixies, the glass envelope of a VFD is evacuated rather than being filled with a specific mixture of gases at low pressure.
Citing dissatisfaction with the aesthetics of modern digital displays and a nostalgic fondness for the styling of obsolete technology, significant numbers of electronics enthusiasts have shown interest in reviving Nixies.
[15] Unsold tubes that have been sitting in warehouses for decades are being brought out and used, the most common application being in homemade digital clocks.
[10] This recent surge in demand has caused prices to rise significantly, particularly for large tubes, making small-scale production of new devices again viable.
