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High Temperature Refractometers

Electronic heating and cooling automatic refractometer for high temperature applications....


The GPR 12-70E is a general purpose model, specially designed to measure the Refractive Index (RI) or Brix of samples of a wide range of temperatures from about 20°C upwards and is especially suited to high temperature measurements up to 100°C.

Temperature control is by internal solid state Peltier cells and so there is no need for a separate thermocirculator. Even when the sample is 100°C, the sample cover remains cool to the touch. Removing the need for a thermocirculator saves a significant amount of bench space, reduces maintenance problems, provides a safer system as there are no pipes carrying hot fluids and removes the uncertainty in temperature between the external device and the actual sample temperature.

The GPR 12-70E refractometer has Peltier cells located below the prism and also above the sample presser, ensuring all round temperature control. It is essential to control the sample cover as well as the prism to obtain accurate, uniform, sample temperature in the widest range of ambient conditions.


Designed to conform to the strictest requirements of today's modern analytical laboratory, the GPR 12-70E is ideal for any laboratory that has stringent analysis regulations in place, whether this is in the oil, pharmaceutical, plastics or food industries. The wide temperature range from about 20°C to 100°C and the wide RI range from 1.33 to 1.70, make the GPR 12-70E the best choice for the crude oil and petrochemical industry. It is also ideal for measuring samples such as polymers, jams and preserves, vegetable oils, confectionery boiling, glucose, speciality chemicals etc.


The GPR 12-70E is a versatile and robust instrument appropriate for either the laboratory or factory environment. A small sample volume, about 0.2 to 0.3ml, is all that is required for accurate measurements. The user can select operating modes to suit either their research or their daily quality control analysis routines. The refractometer can be optimised for both clear and turbid samples such as emulsions. Set-up functions can be protected against unauthorised access or interference. Data can be output to a printer and a computer. As well as the reading, the time, date, temperature, instrument serial number and a sample number can all be recorded. "Data Aquisition" software is available from Index Instruments to interface the output data with spreadsheets or text software on your computer to allow you to perform any required calculations and storage of data. The GPR 12-70E also stores up to 100 readings within the instrument, allowing you to scroll back to look at your previous readings, print any of the readings or download to a computer when convenient. A barcode reader is available as an optional accessory to add coded data to the GPR 12-70E output. The instrument can also be integrated into automatic systems.

Reliable and Versatile

The system is fully solid state ensuring excellent reliability and low maintenance. The prism material is synthetic sapphire, almost impossible to damage. If the long life source lamp fails within three years, we will supply a replacement free of charge.

It is simple to switch the displayed reading from refractive index (RI), to Brix (sugar%), temperature corrected Brix or special 'user' scales. The operator can enter a temperature coefficient and reference temperature to produce a temperature corrected RI scale or, alternatively, generate a complete calibration, via the keypad, against his own set of standard samples. This high temperature model measures RI by back reflection from the sample, which means coloured, dark and turbid materials can be measured as well as clear samples.
The instrument can also be integrated into automatic systems.

Technical Specifications Download Brochure

The GPR 12-70E is ideally suited to the oil industry where refractive index (RI) measurements are often made at temperatures in the region of 75°C or above because of the high viscosity of the samples at lower temperatures.

The GPR 12-70E conforms to the following ASTM standards particularly pertinent to the oil industry

  • D1747, measurement of RI of viscous hydrocarbon liquids and melted solids at temperatures of 80°C to 100°C
  • D1218, measurement of RI of transparent and light coloured hydrocarbons at temperatures from 20°C to 30°C
  • D2140, measurement of RI to include in the  calculation of the carbon-type composition of an oil
  • D5006, test method for measurement of fuel system icing inhibitors in aviation fuels

Index Instruments USA

Tel: +44 (0)1487 814313 Fax: +44 (0)1487 812789
Index Instruments Ltd. Bury Road Industrial Estate, Old Station Road,
RAMSEY, Huntingdon, Cambridgeshire, PE26 1NF, England

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