Quote:
Originally Posted by sphelps
4 - The resent outburst of concern regarding inaccurate refractometers seems more of a myth (exaggerated from fact) and now many companies are releasing new seawater refractometers, some digital some not but always with the promise of more accuracy and a significantly higher price tag. It just seems more of a marketing ploy to me.
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Is this comment based on any documented evidence or just your personal experience along with the
few others that have reported the same?
At least for the point of view that a seawater and a NaCl refractometer produce different results, there is documentation out there, and the fact that Dr Randy Holmes-Farley confirms that it is different, then that is more convincing to me than a hobbyist's anecdotes.
Randy has tested many refractometers and found errant results from many so those particular ones are only accurate at the range they are calibrated for.
This can be true even for seawater refractometers. Generally, but not exclusively, the higher priced ones will be more likely to be more accurate.
Maybe your refractometer is an errant NaCl refractometer that just lucked in to be errant in a way as to be accurate through the range. Like I said before though, it's impossible for an NaCl refractometer and a seawater refractometer with true prisms respectively, to give the same results throughout the scale even if both are calibrated with the same calibration fluid. The refracting prisms in each case are different.
The shortest explanation of how they work should suffice and can be found
at Refractometry Theory and
Abbe Refractometer
Also, while inaccuracies can exist in conductivity meters as well as refractometers, science basically uses conductivity over refraction as they prove to be more reliably accurate.
This link is merely an "interest" link some might find interesting, especially if they teach school.
Refractometer