A gas-filled tube, also known as a discharge tube, is an arrangement of electrodes in a gas within an insulating, temperature-resistant envelope. Although the envelope was typically glass, power tubes often use ceramics, and military tubes often use glass-lined metal.
Gas-filled tubes operate by ionizing the gas with applied voltage to start electrical conduction. Both hot cathode and cold cathode type devices are encountered. Depending on application, either the glow from the gas or the arc discharge may be the desired function.
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Switching gas-filled tubes
Some important examples include the thyratron, krytron, and ignitron tubes.
Lighting and display gas-filled tubes
Fluorescent lighting, CFL lamps, mercury and sodium discharge lamps and HID lamps are all gas-filled tubes used for lighting.
Neon lamps and neon signage (most of which is not neon based these days) are also low-pressure gas-filled tubes.
Specialized historic low-pressure gas-filled tube devices include the Nixie tube (used to display numerals) and the Decatron (used to count or divide pulses, with display as a secondary function).
Xenon flash lamps are gas-filled tubes used in cameras and strobe lights to produce bright flashes of light.
The recently developed sulfur lamps are also gas-filled tubes when hot.
Other types of gas-filled tubes
A type of gas-filled tube called the Geiger-Müller tube is used to detect and measure ionizing radiation.
One of the proposed designs for a fusion reactor is basically a gas-filled tube, the Farnsworth-Hirsch Fusor.
A tube in which electrons move through a vacuum (or gaseous medium) within a gas-tight envelope is called an electron tube.
Gas-filled tubes are used for overvoltage [such as lightning] protection on telecommunications circuits. When the voltage exceeds the firing voltage, the tube conducts, limiting the voltage across it. The three-element [tip, ring, ground] version ensures that there is no voltage differential across the two halves of the pair.
See also
External links
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