Refractometer Calibration

DarthOcellaris · 12-13-2007, 06:56 PM

Do I need to buy a special solution to calibrate or can I use tap water? I was told RODI water was TOO pure to use..is this true?

I've had my meter for a year now and want to calibrate it.

VWD · 12-13-2007, 07:01 PM

I use distilled or RO water, Not tap. You want it pure,

You need to do it more then once a year also,

DarthOcellaris · 12-13-2007, 07:09 PM

so using ro water IS ok? I thought so...take a wild guess at what type retail store told me that

Thanks

VWD · 12-13-2007, 07:12 PM

Thats what I use and have also used distilled , Come out the same, But I also have a TDS meter on my RO/DI and have 0 tds

know-it-all · 12-13-2007, 08:05 PM

as a fish club, we made up a gallon of salt mix using a recipe using this
http://reefkeeping.com/issues/2004-06/rhf/index.php

we found it a bit more accurate than just RO water

DarthOcellaris · 12-13-2007, 08:46 PM

Great read KIA

and long as hades LOL

Fly Guy · 12-13-2007, 09:32 PM

distilled ro water can still be off several points. You can make a solution as was stated or just spend $5 and 60 seconds worth of effort online

http://www.marinedepot.com/ps_ViewIt...n~vendor~.html

DarthOcellaris · 12-13-2007, 10:00 PM

Thanks Bill

I was leaning toward a premade solution anyway...I didn't know they were so cheap though

tims · 12-14-2007, 05:41 AM

the thing with RO water.
the charge in the water is off because of it being RO. the Ph is also not stable. having a known SG is the best way to go.

Loverotties · 12-14-2007, 05:56 AM

Distill is supose to be 0 TDS ,so you cal. to that.

Fly Guy · 12-14-2007, 02:53 PM

Quote:

Originally Posted by Loverotties

Distill is supose to be 0 TDS ,so you cal. to that.

too bad this has nothing to do with it

tdwyatt · 12-14-2007, 03:20 PM

Usually the difference between true accuracy and a good approximation is the difference between using either a standard with a known SG or distilled water,USP and using RO/DI, as many TDS meters, even at zero reading, still allow for a conductivity of 17 or so mSm, definitely still not truly distilled water, and unfortunately, Dept of Commerce allows some variation in selling what can be labled as distilled water without it being distilled water, USP. Although I suggest for most refractometers that folks use distilled water, to be truly accurate and on target, using the $5 product from http://www.marinedepot.com/ps_ViewIt...n~vendor~.html
as suggested by Bill is about the only way to get to true calibration for those acquiring distilled water outside the lab standards arena.

Then again, I usually use a swing arm refractometer to mix ASW until I get to the final stages...

HTH