Wide Range Refractometer J257 with Extended Measurement Range

The Rudolph Research J257 Wide Range Refractometer was developed by working together with laboratory refractometer users from the polymer, petroleum,  petrochemical, pharmaceutical and essential oil industries. The J257 is a fully Automatic, Digital Refractometer, featuring electronic cooling and heating with an extended Refractive Index (RI) measurement range. The J257 is part of the Rudolph Research Rudolph Research Refractometer Product Line.

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Digital Refractometer for a Wide Range of Applications

Rudolph Research’s J257 is designed as a multipurpose automatic refractometer for a broad range of (RI) refractive index measurement applications.  Many laboratories need the versatility of a wide range refractometer as they measure many varied samples. The J257 measures the widest possible range of Refractive Index from 1.26 to 1.72 RI, which means that this instrument can measure many materials that a refractometer with only a food refractive index range of 1.33-1.53 cannot.

Automatic Digital Refractometer Operation

Operating the Rudolph J257 is as simple as placing a sample on the prism, closing the cover and reading the results on the digital screen — all in just a few seconds. Being fully automatic there 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 J257 automatically waits until the sample has been heated or cooled to a predefined temperature before initiating a measurement.

Digital Refractometer With An Easy To Read LCD Interface

A large 7.5cm x 10cm cold cathode fluorescent back lit, digital 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 touch screen panel that will not wear out or get misplaced like traditional or detachable keyboards. The durable touch screen is resistant to fingernails, sharp objects, chemicals, and acids.

Versatile Data Storage Options

The J257 Refractometer offers various data storage options to meet the needs of any lab and any compliance requirement. With 32mb of on-board memory the J257 can work on a stand-alone basis or memory sticks can be utilized to expand memory or make data easily transportable to a PC. The J257 is easily connected to your network or may be linked with a PC. For all data storage options see: Refractometer Data Storage

A Refractometer with Dual Temperature Control System

Unlike other temperature controlled refractometers, the J257 digital refractometer 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. Depending on options, the sample cover can also be used to initiate measurement. This means that the operator never even needs to touch the refractometer screen on a day-to-day basis, simply lower the cover and measurement starts automatically.

Wide Range Refractometer Sample Cover

Optional Sample Presser

The J257 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 refractometer’s measurement prism. This feature offers improved refractive index (RI) readings on a wide range of often hard to measure samples.

Refractometer with Sample Well Cover

J257 Refractometer offers full and Traceable Calibration

The Rudolph J257 Refractometer offers 1 pt, 2 pt, 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.

User Configurable

Versatile laboratory instruments have the advantage of being able to display a lot of information, however this versatility can also lead to confusion, with extra buttons and by forcing the operator to interpret extra information that may have no relevance to their application. The J Series customizable digital refractometer, display allows the instrument to be configured to exactly what is required for each application. The customizable keypad can be “locked out” or just a few keys can be operable, i.e. the measure key, print key, zero key, customer specified sample keys or any combination thereof. The lockout function, calibration and other functions are all password protected.

Refractometer Sample CoverRefractometer Sample Well East To Clean



The Rudolph J Series refractometers are rugged, laboratory instruments offering a sapphire prism for high mechanical and chemical durability. The sample well is made of 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.

Refractometer Options and Accessories

  • NIST traceable calibration liquids
  • IQ/OQ/PQ package
  • Acid resistant sample well and plate
  • Printer
  • Pre-programmed custom scale
  • Data capture software
  • Small volume, easy to clean sample well
  • Different measurement wavelengths
  • Barcode reader


Return to view the entire Rudolph Research Refractometer Product Line


All Rudolph Instruments carry our exclusive 20 Commitment to service your instrument.

Rudolph Research Analytical offers a comprehensive range of Preventive Maintenance and Service Programs. Rudolph has demonstrated a commitment to its customers by keeping installed instruments operational, not only for 20 years, but in some cases for over 40 years. This long-term commitment to keeping our instruments running makes the cost of ownership, over the life of a Rudolph Instrument, one of the lowest in the laboratory market segment. At the date this document was published, there is no other laboratory instrument manufacturer guaranteeing service and technical support for 20 years. View the entire 20 Service Guarantee. 


Wide Range Refractometer J257 – Specifications

J257 Digital Refractometer Specifications
Measurement Scales

Refractive Index (RI)
BRIX (% sucrose)
Temperature Corrected BRIX
Temperature Corrected RI
100 User Programmable Scales

Measurement Range

1.26 - 1.72 RI,
0 - 100 BRIX


Refractive index ±0.0001(Standard), ±0.00001 (Optional)
BRIX ±0.1(Standard), ±0.01 (Optional)


±0.0001 RI,
±0.1 BRIX


±0.0001 RI,
±0.1 BRIX

Optical Wavelength

589.3nm (other wavelengths available)


Industrial Sapphire

Light Source

Light Emitting Diode (est. life: >100,000 hrs.)

Response Time

Continuous readout or user programmable delay (i.e. a 25ºC sample can be cooled to 20ºC and measured in 20 seconds)

Communication Interface

RS232 ports
Cat5 Network (Ethernet)

Analog Control

0-10 volts, 4-20 mA

Temp. Control Range (within 10C of ambient)

10ºC - 100ºC
*other temperature control options are available - 5ºC – 110ºC available with temperature boost option.

Temp. Sensor Accuracy


Ambient Temp. Limit

5ºC - 40ºC

Temp. Correction Range

4ºC - 95ºC (for pure sucrose solutions)

Temp. Control

Prism surface and presser


1, 2 or full multi-point calibration

Operating Dimensions

L: 15.25"  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