Refractometer Calibration

[Capt. Nemo]

What is the best way to calibrate a refractomer? With RO/DI water or with a calibration solution? I have a captive purity refractometer, model RHS-10ATC.

Thanks,
Gary

 

[Paintbug]

this should help.
http://reefkeeping.com/issues/2006-12/rhf/index.php

its best to calibrate the refractometer at the point its being used. somewhere around 1.025 SG. Pinpoint brand of calibration fluid is the only one i know of that works as a reflective index fluid. the article explains more.

 

[Pennoyer]

http://reefkeeping.com/issues/2006-12/rhf/index.php

The easiest way to do so is to order some of the pinpoint salinity calibration solution and test it. It should measure right at 1.026 (it is actually ~1.0254). First test RO/DI and set to 0, then test the cal solution and adjust to 1.026 and you're good to go. Mine measured low when testing the cal. solution, a finding which has also been reported by others with this type of refractometer. HTH

 

[Pennoyer]

Must have been posting at the same time, but you get the idea.

 

[Capt. Nemo]

Thanks everyone! Is this it?

PINPOINTâ"žÂ¢ Salinity Calibration Fluid
53.0 mS standardized fluid for calibrating the PINPOINT Salinity Monitorâ"žÂ¢

 

[mg426]

I believe that is the stuff, best of luck.

 

[Capt. Nemo]

Thank you.

 

[wlagarde]

Another way would be to weigh out 3.4 grams of synthetic sea salt on an analytical balance and qs up to 100 mL with DI water. This would generate a 34ppt solution of salt water for use as a test reference solution.

 

[Tang Salad]

<a href=showthread.php?s=&postid=9227739#post9227739 target=_blank>Originally posted</a> by wlagarde
Another way would be to weigh out 3.4 grams of synthetic sea salt on an analytical balance and qs up to 100 mL with DI water. This would generate a 34ppt solution of salt water for use as a test reference solution.

That's the best alternative I've seen yet. The other formulas require very large amounts (liters) of water.

How accurate is this, and will any brand of salt work?

Many Thanks!

 

[jmicky41]

I tried Randy's recipie with the coke bottle and mortons salt and then bought the Pinpoint solution. Randys and the pinpoint gave exactly the same reading on my cheapo "blue" refractometer.

 

[wlagarde]

<a href=showthread.php?s=&postid=9227804#post9227804 target=_blank>Originally posted</a> by Tang Salad
That's the best alternative I've seen yet. The other formulas require very large amounts (liters) of water.

How accurate is this, and will any brand of salt work?

Many Thanks!

If you use the brand of salt that was used to make up water for the tank, an electronic balance with good precision, and a graduated cylander, then it will be very precise.