Model J357 has a range between 1.26 to 1.72RI and 0 - 100Brix. The accuracy is +/- 0.00004RI / +/-0.03Brix. The resolution is 0.00001RI and 0.01Brix. The temperature control range is between 15 deg C to 100 deg C and with temp. boost option it would be between 10 to 120 deg C. The communication interface is through 2 RS232 and one parallel printer port.

J357 is equipped with live reading and trend analysis feature. These allow the users to easily and quickly see how a process is going and reach to even minor deviations.

Many custom scales can be built in this machine. The setup can be done in a few minutes by entering 2, 6 or 10 data points of concentration and corresponding RI value. Then we need to press Compute and the instrument creates a new custom scale. The customs scale could also include Butyro which is a calculated value from RI.


Designed as a research quality instrument the J357 has the highest performance of any Refractometer in the Rudolph range. This instrument offers the same extra wide range as our chemical industry refractometer models combined with the high accuracy of our food industry refractometer models. It also offers the most powerful temperature control and is able to measure at up to 120 °C.


Operating the J357 is as simple as placing a sample on the artificial sapphire prism, closing the presser and reading the answer -- all in just a few seconds. There are no shadow lines to match and there is no eyepiece requiring any kind of operator determination or manual adjustment. When the "measure when stable mode" is selected, the J357 automatically waits until the sample has been heated or cooled to a predefined temperature before initiating a measurement.

Dual Electronic Temperature Control to 120 °C

Unlike other temperature controlled refractometers, the J357 has temperature control from both above and below the sample. The sample cover is controlled to the same temperature as the prism and, when lowered, is designed to provide a temperature controlled micro environment that provides unrivaled temperature stability, fast measurement time and minimal evaporation. With he Auto Measure option, the sample cover can also be used to initiate measurement.

Optional Sample Presser

The J357 is available with an optional Temperature Controlled Sample Presser that touches the sample. Compared with the standard temperature controlled cover, the optional presser reduces the empty volume of the measurement area thereby decreasing evaporation and at the same time helping to evenly spread semi solid materials over the measurement prism. This feature offers improved performance on many samples.


The J357 offers 1 point, 2 point or a full multi-point calibration. Calibration can be done at 20°C, 25°C or any user selectable temperature within the available range. Regardless of how many times the refractometer has been calibrated, it can always be restored to the initial factory calibration if required.

Custom Scales

The J357 is available with 100 possible programmable scales. Custom scales can be set up in a few minutes. Simply enter 2, 6 or 10 data points of concentration and corresponding RI value, press Compute and the instrument creates a new custom scale.

High Durability Sapphire Prism

The J series refractometer offers a sapphire prism for high mechanical and chemical durability. The sample well is acid resistant 316 stainless steel with a techtron sealing ring. There is no lamp to change, the LED light source is guaranteed for 1,000,000 measurements.

Easy to Clean

alt  Easy to clean Measurement SurfacesNo matter how good a refractometer is, accurate results will only be obtained if the instrument is clean. The Rudolph J Series offers a flat, easy to clean prism that makes this process simple even with sticky sample

Built In 21 CFR Part 11 Compliant Data Storage

The J357 is available with data storage on a removable media card. In 21 CFR mode the data storage system provides a secure password system for storing raw data to comply with FDA specifications. When using non 21 CFR 11 mode the data storage system is a powerful tool for kinetics experiments and excellent system for QA traceability and to help laboratories meet the requirements of ISO and similar quality systems.


A large 7.5cm x 10cm cold cathode florescent back lit graphics LCD allows the scale, sample temperature, set temperature, air temperature, time, date and temperature correction status to be easily viewed. All functions are activated through a touchscreen panel which will not wear out or get misplaced like traditional or detachable keypads. The touchscreen is resistant to fingernails, sharp objects, chemicals, and acids.

No Water Bath Needed


The J357 electronic temperature control means:

  • A significant savings on bench space because the water bath is eliminated.
  • Integrated temperature control where the instrument knows when to measure and records both the Refractive Index measurement and the temperature.
  • Hot liquid from a bath can present a significant danger in the event of a split hose, the J357 doesn't use liquid and thereby eliminates this risk.
  • Eliminating the water bath removes the most maintenance intensive part of a Refractometer. Water baths need to be regularly filled, dosed with algaecide and cleaned.

Traceability & 21 CFR Part 11 Compliance

  • All measurements are made automatically, which eliminates the need for operator judgment.
  • Calibration with fluids traceable to NIST and calibration data securely stored and available for review.
  •  Temperature can be calibrated against a traceable thermometer.
  • Operator Traceability, full 21 CFR Part 11 compliant password system.
  • Verification step with electronic signature.

Permanent Record of All Measurements


Permanent Record of all MeasurementsIn 21 CFR Part 11 mode, all measurements are written to a secure data storage card. Who used the instrument, what they measured and when it was measured is permanently stored on a locked storage media. The media card can also be used to transfer records to a computer for "backup" purposes.

Suitable for a Range of High Demand Environments

  • Petroleum Laboratories where the J357's ability to measure at up to 100ºC without a water bath makes the instrument ideal for ASTM D1218, D1747 and D5006.
  • Research Laboratories where the wide range and high accuracy of the J357 means researchers have the maximum chance of measuring newly synthesized products.
  • Central Research and Reference Laboratories where to have the most accurate results available for setting standards for an organization or a country are needed.
  • Chemical Laboratories can measure more viscous products with a level of accuracy previously available only in narrow range food instruments. 


J357 AUTOMATIC Specifications

Measurement Scales Refractive Index (RI)
BRIX (% sucrose)
100 User Programmable Scales
Measurement Range 1.26 - 1.70 RI,
0 - 95 BRIX
Resolution 0.00001 RI
0.01 BRIX
Reproducibility ±0.00002 RI,
±0.0l5 BRIX
Accuracy ±0.00004 RI,
±0.03 BRIX
Optical Wavelength 589.3nm
Prism Artificial Sapphire
Light Source Light Emitting Diode (est. life: >100,000 hrs.)
Response Time User configurable -- generally less than 30 seconds
Communication Interface Two RS232 ports
One parallel printer port
Analog Control 0-10 volts, 4-20 mA
Temp. Control Range 15ºC - 100ºC
10ºC - 120ºC (optional)
Temp. Sensor Accuracy ±0.05ºC
Ambient Temp. Limit 10ºC - 40ºC
Temp. Correction Range 18ºC - 80ºC (for pure sucrose solutions)
Temp. Measurement & Control Prism surface and presser
Calibration Using water or NIST traceable standards
Operating Dimensions L: 15.5"  W: 10"  H: 4.5"  / 23 lbs.
Shipping Dimensions L: 26"  W: 21"  H: 16" / 30 lbs.
Power Requirements 100-240 volts, 50 Hz - 60 Hz
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