Refractometer Selection Guide from Rudolph Research Analytical

Our Refractometer Selection guide can assist you in determining the requirements for your application and an instrument that will be a good fit for your lab. Rudolph Research designs and manufactures Automatic, Digital, Benchtop, Refractometers to meet the standards of the most demanding laboratories around the world. Our capable instruments offer features not offered by any other manufacturer and will meet with your requirements across a wide range of industry applications. You may use this guide or call one of refractometer specialists to select the right instrument for your needs.

10 Refractometer Models in various configurations, for your industry and application.

Every industry including Food, Beverage, Fragrance, Sugar milling, Refining, Processing, Petroleum, Chemical, Pharmaceutical, Flavor, Cosmetics, and Toxicology testing, has its unique application requirements, environmental constraints and operator handling issues with which to contend. It is for this reason, that Rudolph Research has more than 10 different automatic, benchtop, digital, refractometers with various model configurations for high throughput, high accuracy applications, across various industries to ensure that we have the right refractometer solution for your laboratory situation.

Wide-Range, High Accuracy Refractometers for Pharmaceutical, Toxicology, Flavor, and Fragrance Labs.

Maybe you need a wider range instrument for a pharmaceutical industry application and looking for an instrument which can measure below the standard food Refractive Index (RI) range of 1.33 – 1.53 to comply with the USP monograph for Sevoflurane (refractive index range of 1.2745 – 1.2760) or other halogenated ethers and pharmaceuticals measuring below 1.3 RI. Maybe you’re a flavor, fragrance or essential oil manufacturer or blender dealing with Cinnamic Aldehyde or the many products in this industry having a Refractive Index (RI) greater than 1.60 RI.

Possibly your main concern is not the available range of measurement but the reproducibility of results — just listen to what one of our customers has to say after switching to a Rudolph instrument after years with another brand:

Laboratory Refractometer - J357


“Just wanted to let you know how pleased our company is with the J57HA Automatic. We currently have two of the instruments in service in our sugar testing laboratories and are in the process of ordering three additional refractometers. Before the decision was made to switch our laboratories to the J57HA, rigorous testing was done on the instrument over the past year in our Quality/Research Laboratory.



It has been our policy when doing research type work, using our old refractometers, that we place a sample on the prism, set a timer for two minutes, then press the “Read” button until we get three readings in a row that are identical (this could take up to 12 readings). With the J57HA instrument, we place the sample on the prism, press the “Measure” button and in about 15 seconds we have a stable number. The instrument is so stable in fact, that I can honestly say after using the instrument for over a year, we have never had a different reading from the original measurement, no matter how many times we repeatedly press the “Measure” button.”

— R.R., Senior Process Chemist, Western Sugar Cooperative

How to Use Rudolph Research Analytical’s Guide to Benchtop Refractometers and Industry applications

Although there are many common complications in taking accurate readings that are similar across all industries: like sample cleaning, sample cross contamination, dirty prism, improper water zero, some problems are unique or have a different level of importance to a particular industry. This guide to Rudolph’s line of electronic laboratory refractometers will allow you to see which instruments are best suited to your industry and why. Just select the category that best reflects your industry and then contact us to help solidify your model selection. Our technical sales representatives understand that the initial price is an important part of the purchasing decision but only part of that decision; equally, if not more important is purchasing an instrument that works as intended for the application, and meets all relevant standards, regulations and requirements in the area in which you work.

Refractometers with The Rudolph Research Advantage

Below are a few of the reasons demanding laboratories replaced their older instrument with a J-Series digital bench top instrument from Rudolph Research Analytical.




 refracto-problem-1You are tired of arguments over shadow-line interpretation on your Abbe refractometer . One person says the material is on specification, one person says it’s not. In addition, scratches on the glass prism make visual interpretation even more difficult. The digital J-Series benchtop Internal Reflection instruments use scratch proof artificial sapphire prisms that measure the reflected light and not the transmitted light, like the Abbe, so dark samples measure as easily as clear samples. Just put a drop of sample on the prism, press measure, and walk away. No shadow line, no manual balancing or interpretation. When readings are critical to your end product a quality bench-top instrument from Rudolph Research in your laboratory saves you time and concern over inaccurate readings.
refracto-problem-2Waterbath maintenance is costly and time consuming. Theoretically it should be easy — just top it off with water every week, clean it out and add new algaecide once a month. So why does the bath always seem to be low on water and covered with green slime?  The J-Series automatic refractometers have an electronic peltier temperature control solution that has antiquated water bath systems. Select your temperature through the touch screen and watch the instrument quickly come to temperature and automatically return a digitally displayed measurement all in one easy step. Your concerns about inaccurate readings due to inconsistent temperature control and time-consuming water bath maintenance issues are a thing of the past.
refracto-problem-3Your old refractometer was great when you bought it but now it is being repaired more and more often while measurement instability wastes time and money. In between repairs you can’t even be sure your current instrument is delivering accurate readings. Our customers say it best:  “This J57HA has greatly reduced our sample time and improved our accuracy. Calibration of the instrument is easy and rarely required. We have had no problems or issues with the two instruments that we currently have in service…
I would highly recommend the Electronic Rudolph J57HA over any other brand of refractometer that I have used or tested throughout my many years working in the sugar industry.”


Why switch to one of Rudolph Research refractometers? Superior temperature control and easy to clean prism

Refractometer Sample Well

Rudolph’s Dual Temperature Control System

Rudolph Research Analytical is the only manufacturer to offer demanding laboratories, electronic temperature control from both prism and presser surfaces. The requirements of an electronically temperature controlled instrument operating close to ambient air temperature are very different from the temperature control requirements of an instrument operating more than 10°C from ambient air temperature. Only the Rudolph J Series is designed to be the perfect instrument for both applications.

Measuring RI or BRIX Close to Ambient Air Temperature

The Rudolph J57’s shallow sample well and presserless design makes cleaning easier than deep well prism designs while still maintaining the high level accuracy you require from an automatic, digital instrument. The deep sample well of competing brands is not needed when there is less than a 10°C difference between the prism temperature and air temperature because the temperature gradient across the sample is small.

Refractometer Sample Well

Measuring RI or Brix Far from Ambient Air Temperature

The Rudolph Research J157J257 , J357  and J457 model’s shallow well with temperature control from both the sample presser and prism surface offer superior temperature control while still maintaining ease of cleaning. Rudolph’s temperature controlled presser creates a mini, temperature controlled environment where the entire sample is held at the measurement temperature. This design minimizes the inaccuracies created by temperature gradients across the sample as deep well prisms fight to control temperature from the prism surface while the air and upper part of the sample have widely divergent temperatures.

Other Manufacturers’ Compromise the Refractometer sample well design

From the pictures below one can see that other manufacturers have to make a compromise with the depth and angle of sample well. Since these manufacturers use one sample well and cover design for both temperature applications, they end up with a sample well that is too narrow and deep. The deep sample well makes cleaning needlessly hard at ambient temperature while failing to provide ideal temperature control when the sample and air temperature are more than 10°C from the desired measurement temperature.

Refractometer Sample Wells

Refractometers that assist the user in validating sample load quality. Introducing “Smart Measure”

Rudolph Research introduced new “Smart Measure” technology in 2010, a first-of-its-kind system designed to assist the refractometer user monitor the sample being loaded in the refractometer sample well. . Smart Measure automatically monitors the refractometer’s sample well and gives the user immediate feedback about the quality of the sample. Incorrect measurements due to improper sample loading are virtually eliminated. Smart Measure works by automatically detecting when the refractometer prism is improperly cleaned, insufficient sample is loaded, or if the instrument is improperly calibrated. Smart Measure is another Refractometer innovation and available in our latest generation refractometer the Rudolph Research J457

Rudolph Research Analytical manufactures automatic, digital, bench-top laboratory refractometers for a wide variety of industries. With over 5,000 laboratory instruments installed in demanding applications worldwide and many still in use for over 25 years, we are well known for our reliability, and quality standards. As perpetual innovators we are known to set the pace in our industry for the design and functionality of bench-top laboratory instruments. Our service and responsiveness come from a deep commitment to integrity that we have maintained for over 50 years. Just ask our customers!

Quality, Innovation, and Integrity with a Global Reach, Rudolph Research Analytical.

Refractometer Selection Guide – Specifications