How to Use a Traditional Analog Handheld Refractometer


Different models of traditional analog refractometers have different internal scales on which to read fluid concentrations. Some instruments have specialized scales that indicate the exact mixture of the sample being tested, while others have an arbitrary unit of measure that works like a shorthand for refractive index measurements.

The instruction manual that comes with each refractometer carefully explains the procedure for comparing refractometer readings to the actual known concentrations or properties of your specific fluid. Trained MISCO technical support engineers are always available to assist you at any time.

How to Take a Reading With a Traditional Analog Refractometer

MISCO refractometers are easy-to-use and require little or no training. They can be mastered by ANYONE in just minutes.

  1. Place a drop of sample on the measuring surface beneath the ViewPoint Illuminator.
  2. Look through eyepiece and press the ViewPoint Illuminator.
  3. Take your reading at the point where the contrast line (difference between light and dark areas) crosses the scale.


How a Traditional Analog Refractometer Works

Light passing through a liquid is slowed compared to the speed it travels in air. So once a fluid sample is placed on the measuring surface of a refractometer, the light passing through it slows and is bent.

The refractometer focuses this bent light on a tiny internal scale. The scale is magnified by the eyepiece lenses so it is easily visible.

The optics are supported by a bi-metal strip that moves lenses in response to temperature changes, ensuring that readings are accurate regardless of temperature.



Traditional Handheld Refractometer (8)

What is the difference between the traditional analog Brix refractometer and the electronic digital handheld for Glycol testing? What are the benefits to having one over the other?

This is a good question. Brix is a measure of sucrose content in a sucrose water solution. There is not a direct linear relationship between Brix and glycol concentration. However, there may be a conversion chart available from your glycol supplier or you can make your own (we do not have conversion charts). Our analog Brix refractometer has a precision of +/- 0.2% Brix. The analog refractometer scale is subjective, meaning that two or more people looking at the scale are likely to report different readings depending how they view the scale. You also need to bring the glycol near your face to take a reading. Brix refractometers are temperature compensated for sucrose not glycol. Lastly, since you need to use a conversion table to manually calculate glycol freeze point, you introduce the possibility of making an error. A Palm Abbe digital refractometer with a scale for glycol would be a much better choice. First, the reading is digital which removes subjectivity from the measurement. Second, you can read directly in the unit of measure you desire, concentration or freeze point. This eliminates conversion errors. Since you place your sample in a well, you do not need to bring the refractometer near your face to read it. Also, a digital refractometer with a glycol scale will have temperature compensation specific to glycol. Lastly, the Palm Abbe digital refractometer has at least twice the accuracy of an analog Brix refractometer.

If you cannot see the shadowline in the refractometer and the whole scale is illuminated, then the sample you are testing is above the range of the refractometer scale.

Unless you have a fluid sample on the measuring surface the inside of the refractometer will appear to be dark and you will not see the scale or a shadowline.

Then don’t shake it – just kidding. A rattle most likely means that one of the internal optical components came loose inside. This is usually caused by dropping the instrument. Please send the instrument to our repair department. There is nothing you can do in the field to repair it. In the future remember that this is a precision optical instrument.

Although we try to make refractometers as rugged as we can, please try to handle them as you would a pair of binoculars or a camera.

Most refractometers have a scale division that is equivalent to water. in the case of a Brix refractometer, it is 0.0 Brix, and on the Glycol & Battery Tester, it is +32°F (0°C). This is the reading you should get when testing water at room temperature. If the reading for water does not equal one of the above values, then you need to recalibrate your instrument.

For more information about our analog refractometers, please see the following page: How to Use a Traditional Handheld Refractometer.

How do I replace the ViewPoint Illuminator on my refractometer? I have a MISCO Glycol and Battery Tester, model number 7084VP+.

The ViewPoint illuminator has a built-in coin cell battery with a ten-year shelf life. It is designed for between 3,000-5,000 fifteen-second uses. In the event the battery dies, just send your entire refractometer to MISCO, and we can replace the ViewPoint for you. You may also order a replacement online and change it yourself. Do not try to disassemble the ViewPoint, there are no user serviceable parts inside.

For PDF instructions on how to replace the ViewPoint Illuminator, click HERE

To activate the light on the ViewPoint Illuminator gently press the spot on the label marked “PRESS FOR LIGHT.” Remember there are no dumb questions. If the light doesn’t work, the battery may be dead. If this is the case, please send the instrument back to us and we can replace the ViewPoint.

For more information about our analog refractometers, please see the following page: How to Use a Traditional Handheld Refractometer.


The 7084VP+ (orange body) is the MISCO Glycol and Battery Tester. The battery for the light-source on this refractometer is contained in the ViewPoint Illuminator, a hinged coverplate, on the front of the refractometer. The ViewPoint Illuminator is completely sealed and cannot be opened. Although you cannot change the battery itself, you can purchase a replacement ViewPoint Illuminator. Just look for “ViewPoint” in the refractometer accessories category on this site. The replacement kit comes with complete instructions on how to replace the ViewPoint.

ViewPoint Illuminator for Traditional Analog Refractometer – Replacement Assembly