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A bolometer is a device for measuring the energy of incident electromagnetic radiation. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. It was invented in 1878 by the American astronomer Samuel Pierpont Langley. Samuel Pierpont Langley (August 22 1834 Roxbury Massachusetts &ndash February 27 1906 Aiken South Carolina) was an American Astronomer

It consists of an "absorber" connected to a heat sink (area of constant temperature) through an insulating link. The result is that any radiation absorbed by the absorber raises its temperature above that of the heat sink—the higher the energy absorbed, the higher the temperature will be. Temperature change can be measured directly or via an attached thermometer (composite design). The thermometer is a device that measures Temperature or Temperature gradient using a variety of different principles it comes from the Greek roots

While bolometers can be used to measure radiation energy of any frequency, for most wavelength ranges there are other methods of detection that are more sensitive. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. However, for sub-millimetre wavelengths (from around 200 µm to 1 mm wavelength), the bolometer is the most sensitive detector for any measurement over more than a very narrow wavelength range. Submillimetre astronomy or submillimeter astronomy (see Spelling differences) is the branch of Observational astronomy that is conducted at submillimetre

Bolometers are therefore used for astronomy at these wavelengths. Astronomy (from the Greek words astron (ἄστρον "star" and nomos (νόμος "law" is the scientific study However, to achieve the best sensitivity, they must be cooled down to a fraction of a degree above absolute zero (typically from 50 millikelvins to 300 mK). Absolute zero is the point at which molecules do not move (relative to the rest of the body more than they are required to by a quantum mechanical effect called Zero-point The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic

Bolometers are directly sensitive to the energy left inside the absorber. For this reason they can be used not only for ionizating particles and photons, but also for non-ionizing particles, for any sort of radiation and even to search for unknown forms of mass or energy (like dark matter); this lack of discrimination can also be a shortcoming. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena Radiation, as in Physics, is Energy in the form of waves or moving Subatomic particles emitted by an atom or other body as it changes from a higher energy In Physics and cosmology, dark matter is hypothetical Matter that does not interact with the electromagnetic force but whose presence can be inferred from They are very slow to respond and slow to reset (i. e. , return to thermal equilibrium with the environment). On the other hand, compared to more conventional particle detectors, they are extremely efficient in energy resolution and in sensitivity. They can be used to test very high radio-purity. They are also known as thermal detectors.

The term bolometer is also used in high-energy physics (particle physics) to designate an unconventional particle detector. In experimental and applied Particle physics and Nuclear engineering, a particle detector, also known as a radiation detector, is a device used to They use the same principle described above. The bolometers are sensitive not only to light but to every form of energy.

The operating principle is similar to that of a calorimeter in thermodynamics. A calorimeter is a device used for Calorimetry, the Science of measuring the heat of Chemical reactions or Physical changes as well as Heat In Physics, thermodynamics (from the Greek θερμη therme meaning " Heat " and δυναμις dynamis meaning " However, the approximations, ultra low temperature, and the different purpose of the device make the operational use rather different. Cryogenics is often used incorrectly to refer to Cryonics, cryopreserving humans or animals In the jargon of high energy physics, these devices are not called calorimeters since this term is already used for a different type of detector (see Calorimeter (particle physics)). For Wikipedia jargon see WikipediaGlossary. For hacker slang see Jargon File. In Particle physics, a calorimeter is an experimental apparatus that measures the Energy of particles.

Their use as particle detectors is still at the developmental stage. Their use as particle detectors was proposed from the beginning of the 20th century, but the first regular, though pioneering, use was only in the 1980s because of the difficulty associated with having a system at cryogenic temperature. The twentieth century of the Common Era began on The 1980s was the decade spanning from January 1 1980 to December 31 1989. Cryogenics is often used incorrectly to refer to Cryonics, cryopreserving humans or animals

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Langley's bolometer

The first bolometer used for infrared observations by Langley had a very basic design: It consisted of two platinum strips, covered with lampblack, one strip was shielded from the radiation and one exposed to it. Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 Soot (ˈsʊt is a general term that refers to the black impure carbon particles resulting from the incomplete combustion of a hydrocarbon The strips formed two branches of a wheatstone bridge which was fitted with a sensitive galvanometer and connected to a battery. A Wheatstone bridge is a Measuring instrument invented by Samuel Hunter Christie in 1833 and improved and popularized by Sir Charles Wheatstone A galvanometer is a type of Ammeter; an instrument for detecting and measuring Electric current.

Electromagnetic radiation falling on the exposed strip would heat it, and change its resistance, the circuit thus effectively operating as a resistance temperature detector. Resistance thermometers, also called resistance temperature detectors ( RTD s are Temperature Sensors that exploit the predictable change in

This instrument enabled him to feel his way thermally over the whole spectrum, noting all the chief Fraunhofer lines and bands, which were shown by sharp serrations, or more prolonged depressions of the curve which gave the emissions, and discovered the lines and bands of the invisible infra-red portion. In Physics and Optics, the Fraunhofer lines are a set of Spectral lines named for the German physicist Joseph von Fraunhofer ( 1787

Microbolometers

Main article: Microbolometer

A microbolometer is a specific type of bolometer used as a detector in a thermal camera. A microbolometer is a specific type of Bolometer used as a detector in a Thermal camera. A microbolometer is a specific type of Bolometer used as a detector in a Thermal camera. A thermographic camera, sometimes called a FLIR (Forward Looking InfraRed or an infrared camera less specifically is a device that forms an image using Infrared It is a grid of vanadium oxide or amorphous silicon heat sensors atop a corresponding grid of silicon. Vanadium(V oxide ( vanadia) is the Chemical compound with the formula V2O5 Amorphous silicon (a-Si is the non-crystalline Allotropic form of Silicon. Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 Infrared radiation from a specific range of wavelengths strikes the vanadium oxide and changes its electrical resistance. Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of Radiation, as in Physics, is Energy in the form of waves or moving Subatomic particles emitted by an atom or other body as it changes from a higher energy In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. Electrical resistance is a ratio of the degree to which an object opposes an Electric current through it measured in Ohms Its reciprocal quantity is This resistance change is measured and processed into temperatures which can be represented graphically. The microbolometer grid is commonly found in two sizes, a 320×240 array or less expensive 160×120 array. Both arrays provide the same resolution with the larger array providing a wider field of view. The field of view (also field of vision) is the angular extent of the observable world that is seen at any given moment Larger, 640×480 arrays were announced in 2005.

Cold-electron Bolometer

A cold-electron bolometer uses a SIN(superconducting, insulator, normal metal) junction. The incoming photon i received from a waveguide into the normal metal. It gives its energy to an electron that becomes excited. The significantly increased energy of that electron causes it to tunnel through the narrow insulator layer into the superconductor where it gives rise to a current, that in turn can be measured. The advantage with this is that the absorber is at the same time cooled due to the energy loss.

See also

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Dictionary

bolometer

-noun

  1. (physics) A sensitive device for detecting and measuring the energy of electromagnetic radiation
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