View Full Version : Refractometer Calibration at 20c

09/11/2017, 06:29 AM

I recently made up some calibration fluid, but unsure how to properly calibrate my ATC refractometer. My tank runs at 25c to 26c and my refractometer meter says 20c. Can I calibrate using the calibration standard of 25c?

Did a bit of light reading and still not certain if refractive index varies substantially to worry.

Can someone advice the steps to properly calibrate my refractometer at 20c should I be making a different calibration fluid. Also will this mean the calibration fluid must be 20c evertime I intend calibration. Does the refractometer at room temperature have any bearing on the calibration.

How will a 20c refractometer properly measure my tank considering its 25 to 26c.

Martin Kuhn
09/11/2017, 07:47 AM
Hello Mohammed

Independently from which temperature your tanks water has, the "drop of water" that you apply will immediately adapt to the temperature of your refractometer

If you are sure that your calibration fluid is of the expected salinity and this is around 35 ppm
Your refractometer is one suitable for salt water
-> just calibrate

Good refractometers also have a ATC (automatic temperature correction) that adjusts the psu/SG scale a bit automatically to handle the different reactive indexes of saltwater with varying temperatures of your refractometer

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09/11/2017, 03:15 PM
The 20 C label on the refractometer probably mean that the unit is designed to read as if the sample were at a standard temperature of 20 C, but I can't be sure. The instructions might say somewhere. In any case, for our purposes, if you keep the refractometer at a constant temperature and calibrate it using a refractometer standard, it likely will be accurate enough for our purposes. I would not trust its accuracy very from the calibration point, though. The scales might be biased.

09/12/2017, 01:27 AM
Ok thank you.

Will just calibrate and take it from there.