More stringent requirements of quality control and, in some cases, changing legislation, mean that greater accuracy is being demanded of refractometers. The Abbe 60 Direct Reading models, available in two measuring ranges, have been designed to meet these requirements. The latest designs incorporate an externally mounted LED light source for sample illumination.

A wavelength compensation device is used to ‘achromatise’ to the mean sodium wavelength (589.3nm). Refractive Index can be read directly from a scale divided to 0.001 allowing for estimation to ±0.0001. Temperature control can be achieved by circulation of water; prism temperature is displayed in digital form.

Direct reading models are particularly suitable for the measurement of sugar solutions and sugar content of food and drink products. They can also be used to determine the refractive index of pure liquids, solutions and formulated products including: flavourings, fragrances, oils and fats, solvents, plastics, resins, adhesives and many other industrial chemicals. Instruments come complete with external power supply, standardisation plate and contact liquid, plastic dust cover and instructions for use.

High Accuracy Range of Abbe 60 Refractometers

The high accuracy models are designed for use with monochromatic light sources such as the sodium and spectral source range available from Bellingham+Stanley. A computer program (Windows-based) for conversion of scale readings to refractive index (RI) or Brix (Sugar %) is supplied with each instrument. With good temperature control and use of the micrometer Vernier Scale, an average accuracy of ±0.00004 RI can be achieved across the specified measuring range. Temperature can be controlled by use of a water bath and circulator; prism temperature can be read from the digital display on the instrument.

The high accuracy Abbe instruments offer a dispersion measurement capability: 400 – 700 nm.

The high accuracy Abbe 60 refractometers offer sample illumination by way of reflected light, allowing easier measurement of non-homogenous and opaque samples that are difficult to read under the conventional ‘transmitted’ illumination.

High Accuracy Abbe 60 Refractometers are ideal for use in research and development, quality control and other industrial laboratories where the highest accuracy and precision is often sought. The Abbe 60/ED conforms to the requirements of ASTM D1218 and is used widely throughout the petroleum industry. The Abbe 60/LR offers low range RI measurement of anaesthetics and the such like.

The instruments come complete with digital thermometer, traceable standardisation plate and contact liquid, power supply, sodium D line calibration tables and instructions for use.

Sodium Lamp Outfit

The sodium discharge tube is housed in a height adjustable enclosure mounted horizontally to the lamp outfit base. Sodium bulbs are ideal for regular use as they are relatively inexpensive to purchase and have a working life in excess of 3,000 hours.

Spectral Lamp Outfit

The Spectral Lamp Outfit (pictured right) can be used in conjunction with a number of optional bulbs including mercury, cadmium and helium versions to provide well defined narrow bandwidth spectral lines. The bulb is mounted cap down in the metal shroud, which slides on a vertical post for height adjustment. Spectral bulbs are complex items manufactured specifically for scientific purposes and are both expensive to purchase are short in working life (approx. 200-hours). Interference Filters or software may be used to define specific spectral lines emitted from the bulbs.