Digital Refractometer | J157 PLUS


J157 PLUS available in several models and option configurations.

The Rudolph J157 Digital Refractometer offers high performance and a range of features to suit many demanding applications in laboratories and harsh industrial environments. Rudolph Research Analytical, working together with refractometer (Refractometer) users from various countries and disciplines, has developed the J157 series of Digital Refractometers. The Rudolph J157 benchtop refractometer line combines the features, measurement range, and accuracy that meet the most demanding applications both in and out of the laboratory and shares many features with the Rudolph Research Refractometer Product Line.

Refractometer J157 PLUS

Key Features

  • Easy to clean, shallow Sample well. A clean sample well is imperative to accurate measurements
  • 3-Year Domestic Warranty
  • Lifetime Support Guarantee
  • Modern Refractometer Data Storage
  • Wide Measurement Range for the Chemical Industry
  • Durability to stand up to the harshest environments
  • High Accuracy
  • Most importantly, rugged design as well as small foot print
  • In addition, J57VT offers an wide Refractive Index (RI) measurement range from 1.26 – 1.70


Measurement ScalesRefractive Index (RI) BRIX (% sucrose) Temperature Corrected BRIX Temperature Corrected RI 100 User Programmable Scales
Measurement RangeJ157HA – 1.32 – 1.53 RI, 0 – 100 BRIX J157WR – 1.29 – 1.66 RI, 0 – 100 BRIX
ResolutionJ157HA – ±0.00001 RI, ±0.01 BRIX J157WR – ±0.0001 RI, ±0.1 BRIX
ReproducibilityJ157HA – ±0.00002 RI, ±0.01 BRIX J157WR – ±0.0001 RI, ±0.1 BRIX
AccuracyJ157HA – ±0.00002 RI, ±0.01 BRIX J157WR – ±0.0001 RI, ±0.1 BRIX
Optical Wavelength589.3nm (other wavelengths available)
PrismSynthetic Sapphire
Response TimeUser configurable, can be less than 3 seconds
Communication Interface3 USB, RS232 and Cat5 Network (Ethernet)
Temp. Control Reproducibility±0.002°
Ambient Temp. Limit5ºC – 40ºC
Temp. Correction Range4ºC – 95ºC (for pure sucrose solutions)
CalibrationUsing water or NIST traceable fluids. Factory Default calibration can always be reset.
Operating DimensionsL: 17 1/4″ W: 12″ H: 13″ / 23 lbs. L: 43.5 cm W: 30.5 cm H: 33 cm / 10.4 kg
Shipping DimensionsL: 27″ W: 21″ H: 17″ / 30 lbs. L: 68.58 cm W: 52 cm H: 43.18 cm / 13.6 kg
Power Requirements100-240 volts, 50 Hz – 60 Hz

Rudolph J157

Unique Features and Capabilities
to meet your Application

Operating the J157 PLUS is as simple as placing a sample on the prism, closing the cover and reading the answer – all in just a few seconds. There are no shadow lines to match and there is no eyepiece requiring any type of operator determination or manual adjustment as necessary with ABBE type refractometers. When the “measure when stable mode” is selected, the J157 automatically waits until the sample has been electronically heated or cooled to a predefined temperature before initiating a measurement.

Unlike other temperature-controlled refractometers, the J157 PLUS has electronic 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 an automatic measurement.

The J157 PLUS digital refractometer 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 greatly reducing evaporation and at the same time helping to evenly spread many types of materials including semi solids, and pastes over the measurement prism. This feature offers improved measurement performance on many samples.

The Rudolph Auto Measure Option allows the closing and opening of the presser to start and end a measurement. The operator just closes the cover to start measuring and lifts the cover to stop measuring. The closing and lifting of the lid functions as the start/stop in the measurement process without ever touching the measure button.

No matter how great the refractometer is, accurate results will only be obtained if the prism is clean. All Rudolph J Series refractometers offer a flat, easy-to-clean prism that makes the cleaning process between measurements simple, even with sticky samples.

The J157 PLUS digital refractometer can be supplied with a large range of standard and customized scales. Scales can be customized in a few minutes. Simply enter 2, 6 or 10 points of concentration vs. corresponding RI data. The instrument calculates the custom scale automatically.

The J157 PLUS Digital Refractometer 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.

Versatile laboratory instruments have the advantage of being able to display significant amounts of information. However this versatility can also lead to confusion, with extra buttons and by forcing operators to interpret extra results. These extra results that have no relevance to their application. Above all, the Rudolph J Series customizable display allows the refractometer to be configured to exactly what is required for each application.

The customizable digital keypad can be “locked out” or just a few keys can be operable. For example, the measure key, print key, zero key, customer specified sample keys or any combination thereof. In addition, the lockout function, calibration and other functions are all password protected.

The J series refractometers offer 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. Most importantly, there is no lamp to change, the LED light source is guaranteed for 1,000,000 measurements.


Chemical Concentration Measurements


Many chemicals are sold and shipped as solutions. Both suppliers and end users want to know the exact concentration of the solution. That concentration determines the value of the material and, from a users point of view, how much is added to the process mixture. Refractometers are an extremely quick way to validate starting material purity, measure concentrations, and validate mixture end points. Our rugged instruments can be located in a load out area or beside a production line, not just in a lab.

Why Choose Rudolph

  • Chemical measurement needs temperature control, not correction, and all Rudolph refractometers from the J57 above have this.
  • Confidence in the products you ship to your customers with validated instruments with validated standards and measurement processes.
  • Many solvents have Refractive Indices(RI) outside of the range that a food refractometer can measure; a specialty chemical model is needed.

Typical Rudolph Users

  • Most countries now require that urea solutions be a part of diesel exhaust emission systems. This fluid goes by different names such as Adblue, DEF and ARLA. Manufacturers like YARA and distributors like BRENNTAG use Rudolph.
  • Manufacturers of polymers like Nylon need to monitor raw material solutions. Dupont / Kordsa are just one of many Rudolph users.
  • Urea Formaldehyde and Phenol Formaldehyde resins are critically important to the wood industry. Manufacturers like Hexion and Dynea use Rudolph as part of process control.

Three Choices From Rudolph


Very simple to operate, minimal bench space and a good choice when there is just one dedicated application.


Very wide range so it can measure materials dissolved in fluorocarbon solvents. Flat, easy to clean prism, with on-board concentration programming.


All the advantages of the J357 but operating from a seperate computer allowing easy data transfer to SAP, Excel and similar.



The sugar processing industry uses refractometers across the entire production process. Whether the source is sucrose from sugar cane or sugar beets, or corn based sweeteners our refractometers monitor Brix and Refractometer Dissolved Solids (RDS) in all aspects of our customers processing. Accurate Brix and RDS measurement is a key to process control, and end product purity all which help sweeten the bottom line.

Why Choose Rudolph

  • Very easy to operate for rotating seasonal staff.
  • Temperature control allows the instrument to be calibrated with traceable references to meet ISO and ICUMSA.
  • Flat, easy clean prism means better results even when used with a variety of sugar sample types.

Typical Rudolph Users

  • American Sugar Refining uses many J57 refractometers in both processes and finished product laboratories around the world.
  • Western Sugar uses many J57 instruments in factory labs.
  • Dangote Sugar uses J457 refractometers in factories in Africa.

Three Choices From Rudolph


Very simple to operate, minimal bench space, temperature controlled.


Pour-In design allows for high through put of similar samples with regular prism cleaning.

Autopol 880 & J157

Combined solution for sugar purity measurements.

System Components

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