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An Abbe refractometer is a bench-top device for the high-precision measurement of an index of refraction.
Ernst Abbe (1840–1905), working for Carl Zeiss AG in Jena, Germany in the late 19th century, was the first to develop a laboratory refractometer. These first instruments had built-in thermometers and required circulating water to control instrument and fluid temperatures. They also had adjustments for eliminating the effects of dispersion and analog scales from which the readings were taken.
In the Abbe refractometer the liquid sample is sandwiched into a thin layer between an illuminating prism and a refracting prism. The refracting prism is made of a glass with a high refractive index (e.g., 1.75) and the refractometer is designed to be used with samples having a refractive index smaller than that of the refracting prism. A light source is projected through the illuminating prism, the bottom surface of which is ground (i.e., roughened like a ground-glass joint), so each point on this surface can be thought of as generating light rays traveling in all directions. A detector placed on the back side of the refracting prism would show a light and a dark region.
Over a century after Abbe's work, the usefulness and precision of refractometers has improved, although their principle of operation has changed very little. They are also possibly the easiest device to use for measuring the refractive index of solid samples, such as glass, plastics, and polymer films. Some modern Abbe refractometers use a digital display for measurement, eliminating the need for discerning between small graduations. However, the user still has to adjust the view to get a final reading.
The first truly digital laboratory refractometers began appearing in the late 1970s and early 1980s, and no longer depended on the user's eye to determine the reading. They still required the use of circulating water baths to control instrument and fluid temperature. They did, however, have the ability to electronically compensate for the temperature differences of many fluids where there is a known concentration-to-refractive-index conversion. Most digital laboratory refractometers, while much more accurate and versatile than their analog Abbe counterparts, are incapable of readings on solid samples.
In the late 1990s, Abbe refractometers became available with the capability of measurements at wavelengths other than the standard 589 nanometers. These instruments use special filters to reach the desired wavelength, and can extend measurements well into the near infrared (though a special viewer is required to see the infrared rays). Multi-wavelength Abbe refractometers can be used to easily determine a sample's Abbe number.
The most advanced instruments of today use solid-state Peltier effect devices to heat and cool the instrument and the sample, eliminating the need for an external water bath. The software on most of current instruments offers features such as programmable user-defined scales and a history function that recalls the last several measurements. Several manufacturers offer easily usable controls, with the ability to use from and export readings to a linked computer.
In optics and lens design, the Abbe number, also known as the V-number or constringence of a transparent material, is an approximate measure of the material's dispersion, with high values of V indicating low dispersion. It is named after Ernst Abbe (1840–1905), the German physicist who defined it. The term V-number should not be confused with the normalized frequency in fibers.
In optics, the refractive index of a material is a dimensionless number that describes how fast light travels through the material. It is defined as
Ultraviolet–visible spectroscopy or ultraviolet–visible spectrophotometry refers to absorption spectroscopy or reflectance spectroscopy in part of the ultraviolet and the full, adjacent visible spectral regions. This means it uses light in the visible and adjacent ranges. The absorption or reflectance in the visible range directly affects the perceived color of the chemicals involved. In this region of the electromagnetic spectrum, atoms and molecules undergo electronic transitions. Absorption spectroscopy is complementary to fluorescence spectroscopy, in that fluorescence deals with transitions from the excited state to the ground state, while absorption measures transitions from the ground state to the excited state.
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties.
Spectrophotometry is a branch of electromagnetic spectroscopy concerned with the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength. Spectrophotometry uses photometers, known as spectrophotometers, that can measure the intensity of a light beam at different wavelengths. Although spectrophotometry is most commonly applied to ultraviolet, visible, and infrared radiation, modern spectrophotometers can interrogate wide swaths of the electromagnetic spectrum, including x-ray, ultraviolet, visible, infrared, and/or microwave wavelengths.
Ernst Karl Abbe HonFRMS was a German physicist, optical scientist, entrepreneur, and social reformer. Together with Otto Schott and Carl Zeiss, he developed numerous optical instruments. He was also a co-owner of Carl Zeiss AG, a German manufacturer of scientific microscopes, astronomical telescopes, planetariums, and other advanced optical systems.
Refractometry is the analytical method of measuring substances' refractive index in order to, for example, assess their composition or purity. A refractometer is the instrument used to measure refractive index ("RI"). Although refractometers are best known for measuring liquids, they are also used to measure gases and solids; such as glass and gemstones.
Degrees Brix is the sugar content of an aqueous solution. One degree Brix is 1 gram of sucrose in 100 grams of solution and represents the strength of the solution as percentage by mass. If the solution contains dissolved solids other than pure sucrose, then the °Bx only approximates the dissolved solid content. The °Bx is traditionally used in the wine, sugar, carbonated beverage, fruit juice, maple syrup and honey industries.
Polarimetry is the measurement and interpretation of the polarization of transverse waves, most notably electromagnetic waves, such as radio or light waves. Typically polarimetry is done on electromagnetic waves that have traveled through or have been reflected, refracted or diffracted by some material in order to characterize that object.
The Oechsle scale is a hydrometer scale measuring the density of grape must, which is an indication of grape ripeness and sugar content used in wine-making. It is named for Ferdinand Oechsle (1774–1852) and it is widely used in the German, Swiss and Luxembourgish wine-making industries. On the Oechsle scale, one degree Oechsle corresponds to one gram of the difference between the mass of one litre of must at 20 °C and 1 kg. For example, must with a specific mass of 1084 grams per litre has 84° Oe.
A polarimeter is a scientific instrument used to measure the angle of rotation caused by passing polarized light through an optically active substance.
A refractometer is a laboratory or field device for the measurement of an index of refraction (refractometry). The index of refraction is calculated from Snell's law while for mixtures, the index of refraction can be calculated from the composition of the material using several mixing rules such as the Gladstone–Dale relation and Lorentz–Lorenz equation.
A traditional handheld refractometer is an analog instrument for measuring a liquid's refractive index. It works on the critical angle principle by which lenses and prisms project a shadow line onto a small glass reticle inside the instrument, which is then viewed by the user through a magnifying eyepiece.
A digital handheld refractometer is an instrument for measuring the refractive index of materials.
Inline process refractometers are a type of refractometer designed for the continuous measurement of a fluid flowing through a pipe or inside a tank. First patented by Carl A. Vossberg Jr. US2807976A - Refractometer US2549402A, these refractometers typically consist of a sensor, placed inline with the fluid flow, coupled to a control box. The control box usually provides a digital readout as well as 4-20 mA analog outputs and relay outputs for controlling pumps and valves. Instead of placing the sensor inline of the process, it can be placed in a bypass, attached by a thin tube.
A lensmeter or lensometer, also known as a focimeter or vertometer, is an ophthalmic instrument. It is mainly used by optometrists and opticians to verify the correct prescription in a pair of eyeglasses, to properly orient and mark uncut lenses, and to confirm the correct mounting of lenses in spectacle frames. Lensmeters can also verify the power of contact lenses, if a special lens support is used.
The calculation of glass properties is used to predict glass properties of interest or glass behavior under certain conditions without experimental investigation, based on past data and experience, with the intention to save time, material, financial, and environmental resources, or to gain scientific insight. It was first practised at the end of the 19th century by A. Winkelmann and O. Schott. The combination of several glass models together with other relevant functions can be used for optimization and six sigma procedures. In the form of statistical analysis glass modeling can aid with accreditation of new data, experimental procedures, and measurement institutions.
A measuring instrument is a device to measure a physical quantity. In the physical sciences, quality assurance, and engineering, measurement is the activity of obtaining and comparing physical quantities of real-world objects and events. Established standard objects and events are used as units, and the process of measurement gives a number relating the item under study and the referenced unit of measurement. Measuring instruments, and formal test methods which define the instrument's use, are the means by which these relations of numbers are obtained. All measuring instruments are subject to varying degrees of instrument error and measurement uncertainty. These instruments may range from simple objects such as rulers and stopwatches to electron microscopes and particle accelerators. Virtual instrumentation is widely used in the development of modern measuring instruments.
The DU spectrophotometer or Beckman DU, introduced in 1941, was the first commercially viable scientific instrument for measuring the amount of ultraviolet light absorbed by a substance. This model of spectrophotometer enabled scientists to easily examine and identify a given substance based on its absorption spectrum, the pattern of light absorbed at different wavelengths. Arnold O. Beckman's National Technical Laboratories developed three in-house prototype models and one limited distribution model (D) before moving to full commercial production with the DU. Approximately 30,000 DU spectrophotometers were manufactured and sold between 1941 and 1976.
The operation of a photon scanning tunneling microscope (PSTM) is analogous to the operation of an electron scanning tunneling microscope (ESTM), with the primary distinction being that PSTM involves tunneling of photons instead of electrons from the sample surface to the probe tip. A beam of light is focused on a prism at an angle greater than the critical angle of the refractive medium in order to induce total internal reflection (TIR) within the prism. Although the beam of light is not propagated through the surface of the refractive prism under TIR, an evanescent field of light is still present at the surface.