Page 1 of 1

Using a refractometer

Posted: Fri Sep 05, 2014 7:46 am
by TrevorA
I'm just starting to move my two green spotted puffer tanks to brackish water. So I've got a RHSN-10ATC refractometer but no instructions, however my understanding is that I calibrate it with RO or distilled water and then measure my salted water. Device looks easy to use and calibrate but I don't get the calibration. Am I not measuring the salt difference from my base water? so therefore shouldn't I be calibrating using a freshwater tank sample or even my tap water?

Although having tried calibrating using a freshwater sample my salted water that should be measuring 1.001-1.002 goes under the scale, lol:)

Help please!

Re: Using a refractometer

Posted: Fri Sep 05, 2014 4:45 pm
by Welch4
It is best to use a calibration fuild that is a verified solution at 1.023 usually available through most online marine stores that will carry the refract. If not using calibration fluid it is best to use distilled or and water with 0 TDS ( total disolved solids). Fill the veiwing plate with the fluid your are calibrating with. Looking through the eyepeice turn the screw so the blue/white split lands on 1 if your using distilled and 1.023 if your using calibration fuild.

Re: Using a refractometer

Posted: Fri Sep 05, 2014 7:57 pm
by bertie 83
+1. Calibration fluid is the best way to go. If that's not poss use ro from a reputable place you know and trust as a second best until the fluid is available

Re: Using a refractometer

Posted: Fri Sep 05, 2014 9:27 pm
by Pufferpunk
Calibration solution is to 1.026. But RO should be close enough for BW applications.

Re: Using a refractometer

Posted: Sun Sep 07, 2014 7:36 am
by TrevorA
Thanks :)

Used distilled/purified from the chemist as that is all I could get. Very simple and easy. And I'd got my salt concentrations almost exactly right too, so a very satisfactory start!

Re: Using a refractometer

Posted: Mon Sep 08, 2014 12:04 am
by Master of Puffers
I check my calibration on the frst day of every month with a commerically bought 1.026 standard.

I've found historically in the water treatment industry following ASTM standards that RO water is around 0.997 or 0,998 whch makes for a systemtic error if you are using only a single point calibration on the low end of the sacle.

Given that, we used a mullti-point calibraton along-side an independantly made QC..

Re: Using a refractometer

Posted: Mon Sep 08, 2014 5:13 am
by TrevorA
I can see why you'd do that for a marine tank, and I do tend to go over the top with testing accuracy because that's how I am, but considering the wide range of suitable water for the GSP I don't suppose even a .004 discrepancy would really matter, as long as I only build up slowly and don't cause my filter to cycle.