Nothing could be easier than measuring fluid samples with a MISCO Palm Abbe digital handheld refractometer. This section is for general reference only and is not a replacement for the product instruction manual. Please completely read the instruction manual before using the instrument. If you have lost your manual, duplicate manuals are available for download HERE. Following these steps will help you maximize the precision and accuracy of your measurements.
WARNING! Always read and follow the safety and handling precautions in the Material Safety Data Sheet (MSDS) for the fluid you are testing. Pay particular attention to the recommendations on wearing protective equipment and procedures for sample disposal. If testing body fluids, take precautions to prevent exposure and properly discard the sample after testing.
1. Power On.
If the Palm Abbe is not already on, then press and release the <GO> button to turn it on. If this is the first time you are using the refractometer for the day, if you have just moved between areas with large temperature differences, or if you do not have personal knowledge of its zero-set, then you should zero-set the refractometer before beginning.
2. Select your Scale.
The Palm Abbe digital refractometer is equipped with from one to five scales depending on the model. A scale represents a specific unit of measure for a specific fluid. For instance, a unit of measure could be percent by volume, percent by weight, specific gravity, density, molar concentration, freeze point, boil point, etc. You can select a scale by pressing and releasing the <Menu> button until you see the scale and unit of measure displayed on the LCD display.
3. Apply Sample.
Opening the evaporation cover on the front of the refractometer will reveal the sample well. Inspect the measuring surface to make sure that it is clean and dry, and that there is not any residue left over from previous tests. It may be necessary to use rubbing alcohol with a cotton swab in order to remove certain types of residue. Once clean, place a few drops of sample on the measuring surface using a disposable pipette, making sure that the fluid is evenly distributed and covers the entire measuring surface, and then close the evaporation cover. Disposable pipettes will prevent cross contamination between samples.
In order for the refractometer’s temperature compensation to work properly, and to obtain the most accurate possible readings, the refractometer temperature, the sample temperature, and the ambient temperature should all be in equilibrium. The relative thermal mass of the fluid is small when compared with the thermal mass of the refractometer so it will generally come to the temperature of the refractometer rather quickly, providing there is not a very large temperature difference. Not waiting for the temperature to equalize is the most common error people make. A good rule of thumb is to wait at least thirty seconds for every 20 °F (10 °C) difference in temperature between the fluid and the instrument. You will have to allow more time for fluids above 50 °C and for thick viscous fluids.
5. Take Reading.
Press and release the <GO> button to trigger a reading. In a few seconds your reading will be displayed on the LCD display. It is good practice to take five readings in a row and mentally average the results. If the results are drifting in one direction then the temperature probably is not stable.
6. Clean Refractometer.
When your test is complete, you can use the original disposable pipette to remove the sample and properly discard it. Make sure the measuring surface is clean and dry for the next test. As previously noted, it may be necessary to use rubbing alcohol with a cotton swab in order to remove certain types of residue. A clean sample well is critical to ensure accurate readings.
The Palm Abbe instruction manual has detailed instructions on how to take a measurement, zero-set and span-set the refractometer, and how to care for the refractometer.