Refractometer Calibration Method: Solution or RO?

[gnashty]

I have always used RO to calibrate my refracto, Ive heard alot of people use the 35 ppt calibration solution. I did both and there is a big spread between them, about .006. I even called a couple of LFS looking for some 35 ppt solution - told them what it was for and they said "oh, we just use RO to calibrate ours". And these were pretty decent LFS so Im now confused.

What do you use?

 

[dakota9]

I test it against a known SG, with a Refractometer known to be calibrated

Edit: Although JennM calibrated mine the last time using solution

Edit: RO is the worst way to calibrate

 

[jennm]

I calibrate for free with solution and I also carry the solution.

Back in the day I used to calibrate with RO, and once I caught on to the solution notion a few years ago, I converted. It's the only way to go IMO, because with 35 ppt solution, you are tuning the device more closely to the measurement you wish to take.

Jenn

 

[misu]

Never calibrated mine and I think I still have some solution. If I can't find it I'll come see you Jenn

 

[ichthyoid]

Speaking from personal experience, you always want to calibrate any device, whether it's chemical, electronic, mechanical, whatever, in the middle of the range that you will be measuring.

Reason-
Very few devices are perfectly linear over their range of measurement. Typically, many devices will actually respond with what is called an 'S curve'. So, the ends of the range tend to deviate substantially. Using DI water is calibrating at the low end of the scale/range.

FWIW- I have calibrated hundreds, if not thousands of different devices during my career. I was trained in US Navy PMEL standards, as well as others along the way.

 

[grouper therapy]

rodi without ocd, solution with ocd. hydrometer with cs.

 

[thanh386]

What's cs?

 

[hfleming]

First, excellent question. The fact that you are picking up on this issue shows a good understanding of the measurement side of our hobby.

Ichy is correct. You should be calibrating close to the values you will be measuring. RO will induce a fair amount of error.

 

[grouper therapy]

There was a similar thread a few years back with the same question along with the accuracy of hydrometers. I gathered three different refracs and five individual hydrometers. I calibrated all the refracs with both rodi and solution and tested the hydros with both . None of them was off very much at all. 1.024-1.023 just my experience

 

[db366]

Was told way back when to use distilled water, works just fine for me.

 

[grouper therapy]

Thanh386;707023 wrote: What's cs?

Exactly!

Edit:

grouper therapy;707029 wrote: There was a similar thread a few years back with the same question along with the accuracy of hydrometers. I gathered three different refracs and five individual hydrometers. I calibrated all the refracs with both rodi and solution and tested the hydros with both . None of them was off very much at all. 1.024-1.023 just my experience

The hydrometers were Instant ocean brand

 

[ichthyoid]

If you are going to the effort to 'calibrate', then you should do it correctly. Otherwise, why bother?

Secondly, a sample population of one, or even three, yields a confidence interval of zero.

My point- comparing one (or three) hydrometers or refractometers is statistically meaningless.

Obviously, if your fish don't die, it doesn't matter anyway.

My problem with this argument is the invalid inference:
'I did it with DI water, and that's just as good as using a calibrated solution, and I proved it'

In my world, that's digested hay.

-JMHO

 

[grouper therapy]

ichthyoid;707104 wrote: If you are going to the effort to 'calibrate', then you should do it correctly. Otherwise, why bother?

Secondly, a sample population of one, or even three, yields a confidence interval of zero.

My point- comparing one (or three) hydrometers or refractometers is statistically meaningless.

Obviously, if your fish don't die, it doesn't matter anyway.

My problem with this argument is the invalid inference:
'I did it with DI water, and that's just as good as using a calibrated solution, and I proved it'


In my world, that's digested hay.

-JMHO

You may want to reread if this was in response to my post.
Not an argument Not an attempt at proof Just a statement of my experience, nothing more. Probably no more proof than the two experiences replied to in your thread asking about the blueline 55hd pump . That would yield a confidence interval of zero in my grain fed world.If those two statements are sufficient for you so be it. If you noticed I did use a solution to calibrate and never stated it should not be done.

 

[ralph atl]

http://www.atlantareefclub.org/forums/archive/index.php/t-29652.html">http://www.atlantareefclub.org/forums/archive/index.php/t-29652.html</a>


you need to use a calibrated solution such as pinpoint, as the .....


[IMG]http://reefkeeping.com/issues/2006-12/rhf/index.php#11">http://reefkeeping.com/issues/2006-12/rhf/index.php#11</a>

 

[ichthyoid]

I did not intend to offend anyone with my statements in this thread. If I did so, I would like to apologize.

It's Thanksgiving, and the ARC community is one of the things that I am thankful for in my life (in it's entirety).

Hope that you ALL have a wonderful day!

 

[grouper therapy]

ichthyoid;707211 wrote: I did not intend to offend anyone with my statements in this thread. If I did so, I would like to apologize.

It's Thanksgiving, and the ARC community is one of the things that I am thankful for in my life (in it's entirety).

Hope that you ALL have a wonderful day!

None here I rather handle that type of thing via PM or in person. Just wanted to clarify my intent.

 

[acroholic]

When I used to use an ocular refractometer, I calibrated initially in RODI, then switched to a calibration solution a few months after that. After switching to the calibration solution, I found that if I measured the SG of RODI, the SG read in the negative, like .002-3 units below zero.

Now I use this, and it is one of the best equipment purchases I have made.

http://www.bulkreefsupply.com/store/milwaukee-digital-seawater-refractometer.html">http://www.bulkreefsupply.com/store/milwaukee-digital-seawater-refractometer.html</a>

Usage video:
[IMG]http://www.youtube.com/watch?feature=player_embedded&v=waz1GFLmoVI#!">http://www.youtube.com/watch?feature=player_embedded&v=waz1GFLmoVI#!</a>

 

[lilrobb]

Some food for thought for everyone who swears on calibration fluid:

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here is a salinity map of our oceans - typically we collect specimen (both fish and invertebrate) from different locations on the globe in our aquarium.

As you can see the salinity varies greatly with location.

So whether or not you calibrated your refractometer with RODI, solution or catpee (if you happen to know the salinity of it) - doesn't matter one thing as some of the specimen will be out of their natural salinity levels anyway.

Keeping the salinity level stable (!) is the only requirement.

I had salinity creep up to 1.037 for some months (no ill effects) ad well as drop it to 1.018 (few casualties though).

I am willing to bet that a refractometer "zero'ed" in (as in reading 1.000 when it should read 1.026) will work just as good as one reading 1.026 as long as you are aware that the curernt salinity level in your tank is able to sustain life and you keep it stable at that level...

 

[grouper therapy]

LilRobb;713075 wrote: Some food for thought for everyone who swears on calibration fluid:

alt="" />


here is a salinity map of our oceans - typically we collect specimen (both fish and invertebrate) from different locations on the globe in our aquarium.

As you can see the salinity varies greatly with location.

So whether or not you calibrated your refractometer with RODI, solution or catpee (if you happen to know the salinity of it) - doesn't matter one thing as some of the specimen will be out of their natural salinity levels anyway.

Keeping the salinity level stable (!) is the only requirement.

I had salinity creep up to 1.037 for some months (no ill effects) ad well as drop it to 1.018 (few casualties though).

I am willing to bet that a refractometer "zero'ed" in (as in reading 1.000 when it should read 1.026) will work just as good as one reading 1.026 as long as you are aware that the curernt salinity level in your tank is able to sustain life and you keep it stable at that level...

I agree . I don't care if my salinity is 1.027 instead of 1.023 if I am keeping it relatively stable. I'm not sure why a refrac has to be that accurate. If it drifts it drifts regardless of the calibration method.

Edit: I use a hydrometer most of the time. I know some say they are notoriously inaccurate but with proper cleaning(rinsing with ro water) and use(no bubbles) I have never had them vary from other's solution calibrated Refractometers.

Edit: I DON'T THERE HAS BEEN 23 PACKS OF 35PPT SOLUTION SOLD IN METRO ATLANTA IN THE PAST 12 MONTHS

 

[acroholic]

I believe you should have an accurate calibration regardless where your fish come from, but also agree that salinity stability is more important that chasing 1.025 or whatever.