Abbe Refractometers

Refractometers are measuring instruments which put the phenomenon of light refraction (bending) to practical use. They are based on the principle that as the density of a substance increases (such as when sugar is dissolved in water), its refractive index rises proportionately. Refractometers were devised by Dr. Ernst Abbe, a German/Austrian scientist in the early 20th century. The prism in a refractometer has a greater refractive index than the sample solution. Measurements are read at the point where the prism and solution meet. With a low concentration solution, the refractive index of the prism is much greater than that of the sample, causing a large refraction angle and a low reading. The reverse (lower refraction angle and higher reading) would happen with a highly concentrated solution.
Abbe Refractometers are a type of refractometer used for measuring the refractive index of solid samples, such as glass, plastics and polymer films. There are two detection systems for refractive index: transparent systems and reflection systems. Hand-held refractometers and Abbe refractometers use transparent detection systems, and digital refractometers use reflection detection systems. Abbe refractometer readouts can be either digital or analogue. Abbe refractometers are used most often to measure solid samples – something that standard digital refractometers cannot do. Circulating water baths can be added to control instrument and fluid temperature in Abbe refractometers.
Newer versions of Abbe refractometers have recently been upgraded to include solid state Peltier elements to both heat and cool the refractometer so that you no longer need to use a waterbath. Another modern feature is the ability to link the Abbe refractometer to a computer to control the instrument and to record readings. Some Abbe refractometers can measure at wavelengths other than the standard 589 nanometers, using filters on up to the near infrared range. They are referred to as Multi-wavelength Abbe refractometers. Multi-wavelength Abbe refractometers can be used to easily determine a sample's Abbe number, which is a measure of the material's dispersion (variation of refractive index with wavelength) in relation to the refractive index. These multi-wavelength Abbe refractometers can be used to test eyeglass lenses, contact lens materials, optical plastics for optical communication, compact disk materials and insulating oil. Other accessories that are available include digital printers, extra filters and near-IR viewers.

Author Name: Kathy Brasch : Nationalmicroscope.com

Abbe Refractometers

Brix refractometers

You often hear the term brix and brix refractometer when testing samples for sugar content. Just what is a refractometer? A refractometer is an instrument that measures the refraction of light through a substance. The refractive index becomes higher in a substance of higher concentration.

A refractometer has a wide variety of uses such as measuring sugar concentrations and liquid concentrations. Refractometers are sometimes called “Sugar concentration meters” or “Density meters” depending on the application.
Brix and refractive index are common measurement scales for refractometers. A refractometer that measures brix is referred to as a Brix Refractometer. When measuring solutions that have multiple ingredients the Brix value equals the total concentration of dissolved solids.
About the Brix (%) Scale

Brix (%) shows the concentration percentage of the soluble solids content in a sample (water solution). The soluble solids content is the total of all the solids dissolved in the water, including sugar, salts, protein, acids, etc., and the measurement reading is the sum total of these. Basically, Brix (%) is the number of grams of cane sugar contained in 100g of cane sugar solution. When measuring a sugar solution, Brix (%) should perfectly match the actual concentration. With solutions containing other components, especially when one wants to know the exact concentration, a conversion chart is necessary.

Digital versus Analog Brix refractometers

Brix refractometers are available in hand-held (analogue) or digital models. Hand held units are read by putting a drop of sample on the prism, closing the daylight plate and then reading the scale through an eyepiece as the instrument is held up to your eye. A hand-held/analogue unit determines the refractive index or brix by use of the “Transparent System” which measures light as it passes through the sample and the prism. A low concentration sample has a larger angle of refraction so the boundary line falls on the lower part of the scale, whereas a high concentration sample has a small angle of refraction so the boundary line appears in the upper part of the scale.

Digital Brix refractometers use the “Reflected light system. When you put a sample on the prism and press the Start button, the light that is transmitted from under the sample will travel and refract in multiple directions. The angle of reflection is proportional to the refractive index of the sample, and the reflected light is measured by a sensor and converted into the refractive index or brix readout.

Because of their versatility, brix refractometers are used widely to test sugar content in fruit, vegetables, wine and other food products.

Author Name: Kathy Brasch : Nationalmicroscope.com

Brix refractometers