Refractometers with Electronic Temperature Control


Refractometers with Electronic Temperature Control – PTR range

Incorporating electronic temperature control by Peltier Cell technology…..


The new PTR range of refractometers is the result of a combination of decades of experience in design and manufacture to provide our customers with state of the art refractometers that are accurate, reliable and simple to use. The PTR-300 series of Peltier temperature controlled refractometers comprises two standard models for single application measurement and a third model specifically designed for the sugar industry. Right Hand Side View Brix Scale Redout
All models cover a wide measuring range, as is the requirement of the food, dairy, drinks, pharmaceutical, chemical, petrochemical, flavours and fragrance industries.  The PTR-300 series meets UK, European and US Pharmacopoeia and can be programmed to control data in accordance with FDA regulation 21 CFR Part 11, making it ideal for use in environments such as in the pharmaceutical laboratory.

A full colour programmable touch screen combined with a powerful microprocessor can display readings in a number of popular scales and the simple to use menu format can be displayed in a number of different languages.  Data can be output through either RS232, Bluetooth and USB, allowing connection to printers, computers and a serial output for an auxiliary item such as a bar code reader.

Wide range

All PTR-300 models operate over the wide refractive index (RI) range of 1.32 to 1.68.
The PTR-300 provides an accuracy of 1 in the 4th decimal place of RI over the full range. The PTR-300X model gives an enhanced accuracy to 5 in the 5th decimal place of RI over the range 1.32 to 1.45, with only slightly reduced accuracy to 1.68 RI.

PTR300 Front Shot Screen Brix Scale

Refractive index is measured by the ‘critical angle’ method, similar to the method used in a visual Abbe refractometer. As back reflected light is used, very dark or difficult samples such as chocolate sauce, coffee, honey and dairy products can be measured as easily as clear samples. The PTR-300 series have a special ’emulsion’ mode to improve measurement of turbid samples.  All instruments have no moving parts, an almost indestructible sapphire prism and a sealed casing. They also offer a selection of optional sample cells, making the PTR both extremely versatile and capable of operating in harsh environments.

The PTR range has been engineered to operate in a wide range of ambient conditions. For more extreme conditions, an auxiliary heat sink is available to ensure accurate control when, for example, cold samples are to be measured in the higher ambient temperatures found in tropical climates.


A simple key press on the colour LED touch screen gives access to many popular scales; Refractive Index, Brix, Temperature Corrected Brix, Temperature Corrected RI, Zeiss, Butyro, HFCS(42), HFCS(55), Urine SG, Oechsle, Baume, Babo, NaCl (other scales can be programmed upon request), and up to 16 user programmable scales. You can also have a choice of 4 measuring modes: in ‘Continuous’ mode, the PTR reads in live time updating the display every 2 seconds. ‘Single Scan’ mode allows you to program the instrument to wait a pre-set time to allow for stabilisation and then to scan, display and hold the result. By selecting ‘Autoprint’ mode, the operator can set a time interval for automatic print-outs to monitor a change or flowing sample. In ‘Stability’ mode, the automatic measuring system within the instrument intelligently decides when the sample has come to a stable reading and only then outputs the result. The operator can set the level of stability to ensure that the accuracy required is obtained time after time, in the shortest possible time.

When required, a ‘Qwerty’ format keypad or a numerical keypad appears on screen for data and information entry for ‘GLP’ (Good Laboratory Practice). Time, date and instrument serial number can be output to a printer or PC together with every reading, and the instrument can also be set up to ask for a number, or up to 6 other parameters specified by the user, to fully identify the sample.  The titles of these parameters can have up to 20 characters (letters, numbers or spaces) and so can be in any language.

The new PTR-300 series have a range of special additional features too.  There is a simple routine to set the upper and lower warning limits for a particular material solution.  A second special feature is a routine for programming the instrument to calculate Average and Standard Deviation on readings and produce a small visual graph from the data in real time on the screen.  The PTR-300 series offers a  routine for setting a 2 point zero/scale length adjustment and a simple, one touch key selection for either ‘normal’ or ‘emulsion’ type sample mode.

Bluetooth for wireless connectivity to periphery devices such as PC’s and printers is provided together with USB, RS232 and serial ports at the back of the instrument.  The PTR-300 series can also communicate with Optical Activity’s latest range of polarimeters using Bluetooth technology, please contact Index Instruments for further details.



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Refractometers with Electronic Temperature Control – TCR range

TCR 15-30 Refractometer

The TCR refractometer incorporates electronic temperature control using Peltier cell technology which has been developed by Index Instruments over the period since we first launched a model using Peltier cells in 1996. The TCR has a proven record for reliability and ease of use, both in factories and in laboratories throughout the world.


The TCR is exceptionally easy to use and has been specifically designed to be a robust instrument which anyone, with minimum training, can use to obtain rapid, accurate refractometer measurements of a large variety of samples. The instrument has a single touch-sensitive button on the top plate which the operator uses either to send an output to a PC or printer, or initiate a reading depending on how the TCR has been set to operate. The flat stainless steel top plate makes this instrument particularly easy to clean.

Versatility and Security

The TCR refractometer is also extremely versatile; the analysis parameters are set using an infra-red remote control unit. Having set the unit for a particular analysis, the remote control can then be removed from the working area to prevent, for example, unauthorised alteration of the parameters by production staff. The TCR is therefore ideal for repetitive quality control of a particular type of sample.


Once the scale has been selected (RI, Brix, temperature corrected Brix, etc.), the sample control temperature set, and the sample stabilisation parameters chosen using the remote control, all the operator has to do is apply a few drops of sample, or a small amount if a paste, to the prism and close the cover.

The display panel provides a large clear digits giving the results on an LCD screen. The back-lit display is easy to read in bright light conditions and with a read time of less than 3 seconds, the sample reading is always up-to-date. In continuous mode, the result is displayed instantaneously when the hinge cover is closed. For samples which need time to reach a stable temperature, you can set a delay time from 3 to 999 seconds. As each measurement is made, the result along with scale, time and date is automatically output to a printer or PC if attached to the unit. Alternatively, the TCR can be set to automatically determine when the sample has stabilized and only then display or output the result.

PC Software is available from Index Instruments Ltd. to connect your TCR to data storage, spread sheets or documents on your computer.

Temperature Control

The sapphire prism and surrounding metal are controlled from below using a Peltier cell. Fan cooling is not required and the TCR has no moving parts. The sample cover is extremely well insulated, and once the cover is closed, the small sample volume quickly stabilizes at the control temperature. The most frequently used temperatures in refractometry are 20°C and 25°C and the TCR easily controls at these temperatures to within 0.03°C under normal comfortable ambient working conditions. The TCR can also operate up to a maximum set temperature of 40°C. If you have samples which need to be measured at higher temperatures, it becomes necessary to control the temperature of the cover as well as the prism and so the TCR is not suitable; consider instead the Index Instruments GPR 12-70E which provides electronic temperature control to both prism and cover up to 100°C or the GPR 12-70 or GPR 12-70X which use flowing fluid to control both prism and cover and can operate up to 70°C.


The TCR is a “critical angle refractometer, working by reflecting light from the interface between the sapphire prism and the sample. Even dark and difficult samples such as molasses, coffee, sauce and dairy products can be measured with the same ease and accuracy as clear samples. Alternative sample cells are available for automatic or semi-automatic sampling. Contact Index Instruments for advice.


With only a small ‘footprint’ of less than 24 cm x 24 cm the TCR makes little demand on laboratory working space. Mini-printers are available amongst optional accessories.


The TCR can be supplied, on request, with a UKAS (United Kingdom Accreditation Service) certificate of calibration. Liquid standard samples with UKAS Calibration Certificates are also available for your own calibration checks.

The TCR 15-30 has an internationally recognised IP67 rating for physical impact protection and water resistance and and is manufactured to comply with the European Directives on Electro-Magnetic Compatibility, carrying the internationally recognised CE mark.