Refratcometer/calibration fluid

[Rome]

I have always used RO/DI water and just calibrated my refractometer that way I would just set the dial on 0 with the RO/DI. Well I decided I wanted a more accurate reading or at the very least to see if it was accurate with just pure water so I bought some 53.0/ms calibration fluid.

 

I got the fluid and test my refractometer when I put the 3 drops of the calibration fluid on it read alittle high 38 ppm. So I reset in back down so the calibration fluid read 35ppm. Then I rechecked with RO/DI and it was 3ppm below the 0 on the dial or -3ppm.

 

What should I trust the fluid being right on when I calibrate using it or seeing how RO/DI should read 0 just go with the RO/DI and calibrate it for that. If I go the RO/DI route the meter reads 3ppm higher testing the calibration fluid. The only reason I dont want to trust the fluid 100 percent is that RO/DI should read 0 and when I calibrate using the 53.0/ms fluid, my RO/DI measures at -3ppm the 0 on the dial.

 

Maybe I'm just trying to be to perfect but I'd like my salinity to to as accurate as humanly possible.

[cveverly]

From what I have have been told you should not us RO/DI water for calibrating your refractometer. You want the meter calibrated to the normal range of usage. If you are concerned, have your SG checked by a LFS or someone near you. Then compare that test to your meter.

[StevieT]

Trust the solution.

 

You are calibrating to a specific salt level, not zero. You are measuring salt in your tank, not fresh water. Same as a scale, you do not calibrate it to measure zero but a specific and know weight.