Calibrating a refractometer

cope413 · Jan 17, 2017

jason2459 said:
Maybe

http://reef2reef.com/threads/does-your-calibration-solution-need-calibrated.250133/

No, not maybe. That's why I said, "If you have a known solution of 35ppt"

Enjoy the rabbit hole of questioning calibration fluid.

Not sure why people want to make this more complicated than it needs to be.

wheelman76 · Jan 17, 2017

cope413 said:
If you have a known solution of 35ppt, and your refractometer reads 35ppt for that solution, and your tank water doesn't, you can be confident your tank is not at 35ppt.

It doesn't have to be more complicated than that unless you want it to be. $13 for calibration fluid. Why not just buy a bottle and be done with it?

It's not always that easy , I just bought a brand new bottle of Sybon 35ppt calibration fluid last weekend from my LFS and it told me my refractometer was way off and that my tank was at 1.030. I returned the bottle to my LFS and they tested it and it was 5ppt off. They tested 3 other bottles on the shelf and they were bang on. I find that very frustrating because if you can't trust the calibration fluid then what can you trust ? It's a good thing that I confirmed the fluid was faulty rather than making drastic adjustments to my tanks salinity.

jason2459 · Jan 17, 2017

cope413 said:
No, not maybe. That's why I said, "If you have a known solution of 35ppt"

Enjoy the rabbit hole of questioning calibration fluid.

Not sure why people want to make this more complicated than it needs to be.

And how do you assure your "known" calibration fluid for $13 is really known? So, maybe.

Making your own standard seems to simplify it by taking out that unknown or at least reduces the unknown.

Randy provided in that article I linked to a very simple recipe to make your own.

cope413 · Jan 17, 2017

Right, so make your own. Then you will have a known solution of 35ppt - and my conditional statement will be true.

jason2459 · Jan 17, 2017

cope413 said:
Right, so make your own. Then you will have a known solution of 35ppt - and my conditional statement will be true.

I believe you stated buying a $13 bottle not making one.

$13 for calibration fluid. Why not just buy a bottle and be done with it?

Which my answer to that question is maybe and a link to a thread showing those bottles can be off.

Nemo's Janitor · Jan 18, 2017

@Randy Holmes-Farley... Brands of salt mixes have different "ingredients" in their mix. Is there a reference on the the different salt mix brands, referring to refractive index, comparing to... the Salinity, SG and Density.

Edit... I am referring mostly to salt mixes that are recommended for "fish only" use and those for "reef tank" use

Nemo's Janitor · Jan 18, 2017

For me, over the years, I have found that the calibration of the refractometer is best "CHECKED" and not "ADJUSTED" to your own tank reference solution just before you check salinity. Adjust salinity to correspond to the reference solution/s.

Salinity stability is key. If you are storing samples of your water, and recording progress you can always go back to that sample when tank was running at it's best.

RONBATTLE · Jan 19, 2017

jason2459 said:
Don't worry your e-yelling had my head spinning.

But for how accurate one has to be I don't believe one has to be precisely at 35ppt. It's a good target.

EXCUSE THIS OL MAN, DID NOT THINK MY TYPING IN CAPS WOULD BE CONSTRUED AS E-YELLING....JUST A HABIT...I HOPE THE SPINNING HAS CEASED...UNLESS READING THIS CAUSES A RELAPSE...LOL...

jason2459 · Jan 19, 2017

RONBATTLE said:
EXCUSE THIS OL MAN, DID NOT THINK MY TYPING IN CAPS WOULD BE CONSTRUED AS E-YELLING....JUST A HABIT...I HOPE THE SPINNING HAS CEASED...UNLESS READING THIS CAUSES A RELAPSE...LOL...

FYI, online it is considered yelling and does make it harder to read for some.

Frop · Feb 9, 2017

So because of this thread I bought the calibration solution. Then I put it in. Read the number and it was spot on. Last time it was calibrated was with RODI

but now I have a reference.

jason2459 · Feb 9, 2017

Frop said:
So because of this thread I bought the calibration solution. Then I put it in. Read the number and it was spot on. Last time it was calibrated was with RODI but now I have a reference.

Assuming the calibration solution you bought is correct.