Globar
Encyclopedia
A Globar is a silicon carbide
rod of 5 to 10 mm width and 20 to 50 mm length which is electrically heated up to 1000 to 1650 °C (1,832 to 3,002 F). When combined with a downstream variable interference filter
, it emits radiation
from 4 to 15 micrometre
s wavelength
. Globars are used as thermal light sources for infrared spectroscopy
because their spectral behaviour corresponds approximately to that of a Planck radiator (resp.: black radiator
). Alternative middle-infrared
luminous sources are Nernst lamp
s, coils of chrome-nickel alloy or high-pressure mercury lamps
.
The technical term Globar is an English portmanteau word consisting of glow and bar. Hence, the term glowbar is often used synonymously in the English-speaking area (which is an incorrect spelling in the strict sense).
The American Resistor Company in Milwaukee, Wisconsin
, had word and lettering Globar registered as a trademark (in a special decorative script font
) with the United States Patent and Trademark Office
on June 30, 1925 (registration number 0200201) and on October 18, 1927 (registration number 0234147). This registration had been renewed for the third time in 1987 (by various companies throughout 60 years).
Silicon carbide
Silicon carbide , also known as carborundum, is a compound of silicon and carbon with chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite. Silicon carbide powder has been mass-produced since 1893 for use as an abrasive...
rod of 5 to 10 mm width and 20 to 50 mm length which is electrically heated up to 1000 to 1650 °C (1,832 to 3,002 F). When combined with a downstream variable interference filter
Interference filter
An interference filter or dichroic filter is an optical filter that reflects one or more spectral bands or lines and transmits others, while maintaining a nearly zero coefficient of absorption for all wavelengths of interest...
, it emits radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
from 4 to 15 micrometre
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
s wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
. Globars are used as thermal light sources for infrared spectroscopy
Infrared spectroscopy
Infrared spectroscopy is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light. It covers a range of techniques, mostly based on absorption spectroscopy. As with all spectroscopic...
because their spectral behaviour corresponds approximately to that of a Planck radiator (resp.: black radiator
Black body
A black body is an idealized physical body that absorbs all incident electromagnetic radiation. Because of this perfect absorptivity at all wavelengths, a black body is also the best possible emitter of thermal radiation, which it radiates incandescently in a characteristic, continuous spectrum...
). Alternative middle-infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
luminous sources are Nernst lamp
Nernst lamp
Nernst lamps were an early form of electrically powered incandescent lamps. Nernst lamps did not use a glowing tungsten filament. Instead, they used a ceramic rod that was heated to incandescence...
s, coils of chrome-nickel alloy or high-pressure mercury lamps
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 borosilicate glass bulb...
.
The technical term Globar is an English portmanteau word consisting of glow and bar. Hence, the term glowbar is often used synonymously in the English-speaking area (which is an incorrect spelling in the strict sense).
The American Resistor Company in Milwaukee, Wisconsin
Wisconsin
Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...
, had word and lettering Globar registered as a trademark (in a special decorative script font
Typeface
In typography, a typeface is the artistic representation or interpretation of characters; it is the way the type looks. Each type is designed and there are thousands of different typefaces in existence, with new ones being developed constantly....
) with the United States Patent and Trademark Office
United States Patent and Trademark Office
The United States Patent and Trademark Office is an agency in the United States Department of Commerce that issues patents to inventors and businesses for their inventions, and trademark registration for product and intellectual property identification.The USPTO is based in Alexandria, Virginia,...
on June 30, 1925 (registration number 0200201) and on October 18, 1927 (registration number 0234147). This registration had been renewed for the third time in 1987 (by various companies throughout 60 years).
External links
- Viewgraphs about infrared beamlines and IR spectroscopy Advanced Light Source, San Francisco
- Introduction to the optical principles of IR spectroscopy, light sources Ralf Arnold (in German)