MISCO Refractometer Q&A Forum
Find answers to many common questions concerning applications, operation, calibration, and maintenance of refractometers:
Refractometer Calibration (7)
The MISCO Palm Abbe has a high-precision thermistor that is in contact with the fluid. This thermistor is able to accurately sense the exact temperature of the test sample. The internal microprocessor interprets the signal from the thermistor and applies a correction to the readings based on the temperature difference and percent volume for the fluid under test.
The most amazing feature is that the digital refractometer can utilize multiple temperature correction tables for different fluids over a wide temperature range. A digital refractometer can also be custom programed to measure your specific fluids and can have custom temperature compensation tables as well.
If a refractometer is tested with distilled water and consistently gives 32 degrees as the freeze point, would a certified calibration still be necessary? I am trying to understand how the refractometer could be outside of its specifications and require a certified calibration if it is consistently giving the expected reading with a control fluid such as distilled water. Also, how often does MISCO recommend that the digital refractometer receive certified calibration?
It is possible for a refractometer to read correctly with respect to a distilled water value but be out of calibration on the higher-end (span) of the refractometer. You can tell a better quality refractometer since it has a method of zero-setting to distilled water and also calibrating the span of the instrument using NIST traceable calibration standards. Calibration is the best way to maximize the accuracy of a refractometer. We recommend zero-setting the refractometer at least every day and checking/or setting the span about every month. We also recommend that a refractometer be sent in for an annual certified calibration.
On a Brix and Refractive Index scale, your digital refractometers seem MORE accurate than you claim?!
Please explain why your Palm Abbe refractometer lists accuracy as 0.0001 nD AND as 0.1 % Brix when an interval of 0.1 % Brix is almost exactly 0.0002 nD. Am I right in thinking the Brix % should be changed to 0.05 or the nD to 0.0002, which? I use a refractometer to indicate the concentration of firefighting foam solution, by comparison with calibration samples and most other digital hand held refractometers on the market list accuracy as 0.0002 nD or 0.1 % Brix. Some popular firefighting foams have quite low RI, which results in having typical solution RIs of 1.3330 – 1.3338 nD, and if the accuracy claimed is twice as good as your competitors, the error on readings could be halved. Note: FPEs working with foam systems often have to report on RIs as low as 1.3332.
You caught us! The Palm Abbe digital refractometer actually has better Brix precision than we claim, and here’s why: The actual precision of the Palm Abbe refractometer is +/- 0.0001 nD20. Where “nD” represents the refractive index measured at the sodium D-line (589.3 nm) and “20” represents 20 °C, the reference temperature for the measurement. There is a non-linear relationship between Brix and refractive index. The average change in refractive index for a corresponding 0.1% change in Brix is 0.0002 nD20. The average change in refractive index for a corresponding 0.05% change in Brix is 0.0001 nD20. So why do we claim a precision of +/-0.1 Brix when clearly it should be +/-0.05 Brix? The reason has to do with the Palm Abbe refractometer display resolution. Since the Palm Abbe refractometer only displays Brix in 0.1 increments, in a practical sense, it does not really matter that it is capable of +/-0.05 Brix precision.
I have a customer who has a PA 201 Palm Unit & is using one of our metalworking coolants that has a 3.11 Brix multiplier. He wants to have it calibrated with the Brix multiplier factored in, so that his technicians will read the true concentration as having to use a multiplier. Can this be done and if so, where does it need to be sent? What is the cost for this upgrade? What other information is needed prior to shipment back to MISCO?
We can program any multiplier or factor for a metalworking fluid into the Palm Abbe digital refractometer so that you can directly read the concentration of a metalworking coolant or fluid. This can be done at the time of order or the refractometer can be returned to us for reprogramming.
Can you please kindly advise us if your company manufactures a refractometer with a range of 1.3330 – 1.3340 on the standard refractive index scale and/or 0 to 5 on the Brix Scale.
Scales are currently available for the Palm Abbe digital refractometer that can measure EG (ethylene glycol), PG (propylene glycol), TEG (triethylene glycol), DEG (diethylene glycol), MEA (Monoethanolomine), DEA (Diethanolomine), and DGA (Diglycolamine).
Please contact MISCO customer service for details on ordering, or see the Build-Your-Own section of our website.
Can I load scales onto a MISCO Refractometer once I have received the unit? How does scale programming work?
We have 100s of scales, among them many for ethylene glycol (EG) and propylene glycol (PG) that can be programmed into the Palm Abbe PA203x digital refractometer.
You can select scales for measuring freeze point, boil point, percent by weight, percent by volume, specific gravity, density, and more.
You can get a list of all the standard ethylene glycol (EG) and propylene glycol (PG) refractometers by navigating to the Products>Digital Handheld page on our website and then using the filters to list refractometers with ethylene glycol (EG) and propylene glycol (PG) scales. You may also want to try the Build-Your-Own section of our website and select the exact scales you want.
Pressing the SELECT button will cycle through all the possible scale choices on the Palm Abbe Digital Handheld Refractometer. If you want to permanently change the refractometer scales, you may send it back to us and we will be happy to reprogram it for you for a slight charge.
For more information about refractometer care, maintenance, and troubleshooting, please see the following page: Digital Handheld Refractometer Training.