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.



Digital Handheld Refractometer (12)

You can download a replacement instruction manual in PDF format from our support page. Click on Instruction Manuals

If your instrument won’t power on, check the battery polarity. If the polarity is correct and the instrument will still not power on, change the battery. If it still doesn’t work, call MISCO tech-support.

It is recommended that the instrument be calibrated at least once a day, prior to performing any test requiring the highest precision, or when moving between environments with extreme changes in ambient temperature.

A reading of [ LOW BATT ] indicates the battery needs to be replaced. Make sure you observe the battery polarity when changing the battery.

A reading of [ RANGE +/- ] indicates that the measurement is above or below the range of the current scale. If the instrument periodically reads [RANGE -], make sure you haven’t trapped a small bubble in the sensing area. A bubble directly over the sensing area can cause the instrument to display [RANGE -].

A reading of [ TEMP ] indicates the fluid or instrument temperature is above or below the range of the instrument.

A reading of [ BRIGHT + ] indicates the optical sensor is being overpowered by strong ambient light. If this happens, shade the sensor or move to a less brightly lit area and repeat the measurement.

Pressing the SELECT button will cycle through all the possible scale choices on the instrument. If you want to permanently change the instrument scales, you may send it back to us and we will be happy to reprogram it for you for a slight charge.

The refractometer will power off automatically after three minutes of inactivity. To manually shut off the instrument, hold the ON/CLEAR button down for 3-5 seconds.

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.

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.

The Palm Abbe digital refractometer uses two standard AAA batteries. To change the refractometer batteries, use a Phillips head screwdriver to remove the two battery compartment screws on the bottom of the instrument. The battery door will be visible on the underside of the refractometer even if the refractometer is equipped with a Rubber Armor Jacket ™. When you remove the two screws, be careful not to misplace the tiny O-Ring seals that are attached to them. Discard the old batteries and install fresh ones in the refractometer. Be sure that battery polarity is correct or it will result in irreversible damage to you refractometer. Before reinstalling the door, check the condition of the battery cover gasket. Clean the gasket if it is dirty or contact MISCO sales department for a new battery cover gasket if yours is damaged. Once the batteries are in place in the refractometer, position the battery door and insert the screws. Tighten the screws firmly but do not over tighten.

For more information about refractometer care, maintenance, and troubleshooting, please see the following page: Digital Handheld Refractometer Training.