What Type Of Refractometers Are Best

[Dnahacker]

I think it is important to clarify a few things.. an atc refractometer is automatic temperature compensation, refractive index changes with temperature because the density is different. An atc refractometer normalised to 25 degrees Celsius.

A salinity refractometer (which is what most folks use) is made for measuring brine solutions , that is, sodium chloride solutions, when measuring sea water they will read 1.8 ppt higher than it really is .

 

[Randy Holmes-Farley]

whats the difference between calibrating with something that is 1.00 sg vs 1.026sg?? I guess what im saying if you abosultely know your water is 1.00sg and you zero your refractometer to that solution wouldnt it accurately read anything else?

If it is a perfectly made seawater refractometer, that is correct.

Most sold to hobbyists are not. Most are brine refractometers, and so cannot be calibrated by fresh water and be expected to be accurate for seawater salinity measurement. A perfectly calibrated brine refractometer reads brine (sodium chloride) correctly, but not seawater.

 

[Randy Holmes-Farley]

Do you have to have RO water with you to test everytime?

Some people find they need to recalibrate each time they use their refractometer. Others let it go a bit between calibration.

FWIW, don't use RO water, unless it is a true seawater refractometer. If it doesn't use those words, or something like it, it probably is not and needs a 35 ppt standard (regardless of what the manufacturer claims).

 

[deerhunter06]

If it is a perfectly made seawater refractometer, that is correct.

Most sold to hobbyists are not. Most are brine refractometers, and so cannot be calibrated by fresh water and be expected to be accurate for seawater salinity measurement. A perfectly calibrated brine refractometer reads brine (sodium chloride) correctly, but not seawater.

Is a Milwaukee a perfectly made? It comes with 1.00 to zero the device everytime before use.

 

[shred5]

D-D, redsea, Vee Gee Refractometer are true seawater refractometers. I think Dr Foster and Smith cary a Vital Sine.
Those are the only ones I know of that are true saltwater.

 

[Larry L]

Just to play devil's advocate... Are refractometers that much better than swing arms? Steven Pro did an article in SeaScope a while back that indicated swing arms were just fine:

"If you are careful with the bubbles, these particular hydrometers can be both accurate and precise right out of the box. Don't believe me, check out the testing I did published in the Spring 2008 issue of SeaScope."

 

[shred5]

Just to play devil's advocate... Are refractometers that much better than swing arms? Steven Pro did an article in SeaScope a while back that indicated swing arms were just fine:

Lots of respect for Steven but no... I have had two brand new ones both read different. But that said lab grade hydrometers are fine but they are not swing arm either. From what I understand they are more accurate than a refractometer just harder to read and less convenient in a reef.

 

[Larry L]

Lots of respect for Steven but no... I have had two brand new ones both read different. But that said lab grade hydrometers are fine but they are not swing arm either. From what I understand they are more accurate than a refractometer just harder to read and less convenient in a reef.

Not sure what you'd do with two that read differently... FWIW, he was looking at regular retail stuff, not lab grade. Unfortunateley I can't find the SeaScope article, but I did find part 1 of the writeup here: Hydrometer rev pro

 

[Randy Holmes-Farley]

Just to play devil's advocate... Are refractometers that much better than swing arms? Steven Pro did an article in SeaScope a while back that indicated swing arms were just fine:

When I tested and reviewed some swing arms, they were not OK, regardless of bubbles:

Chemistry and the Aquarium: Specific Gravity: Oh How Complicated! ? Advanced Aquarist | Aquarist Magazine and Blog

from it:

So how do these hydrometers measure up? In my tank the water was measured to be S=35 ± 0.5 by conductivity. Using the Deep Six swing arm hydrometer I got readings of S=32.5 ± 0.5 at 81 °F and S=32 ± 0.5 at 68 °F. Using the SeaTest I got S=34.5 ± 0.5 at 81 °F and S=34 ± 0.5 at 68 °F.

 

[Randy Holmes-Farley]

Is a Milwaukee a perfectly made? It comes with 1.00 to zero the device everytime before use.

Milwaukee makes many different refractometers of various types.

Is there a particular one you are asking about?

 

[deerhunter06]

Milwaukee makes many different refractometers of various types.

Is there a particular one you are asking about?

Ma887 seawater refractometer

 

[deerhunter06]

Pic of it.

 

[Kehaulani]

I was looking at that one

 

[Randy Holmes-Farley]

Ma887 seawater refractometer

That one is a true seawater refractometer, and because of it's design, I think you must use RO/DI to calibrate it. You can, however, check it with a 35 ppt standard if you want.

 

[deerhunter06]

That one is a true seawater refractometer, and because of it's design, I think you must use RO/DI to calibrate it. You can, however, check it with a 35 ppt standard if you want.

Thanks Randy.

 

[Randy Holmes-Farley]

You're welcome.

Happy Reefing.

 

[djbetterly]

I know refractometers and conductivity probes don't read exactly the same, but I need a new backup. Would the D-D or Red Sea suffice for this? I also use it for mixing salt water.

 

[shred5]

One thing to is the calibration solution needs to be new. I got some old stuff once and it read much higher. I also have some older bottles I kept in the basement that read higher than newer bottles?
Randy what would cause this? Does water evaporate in plastic bottles over time or do the bottles degrade?

 

[shred5]

I know refractometers and conductivity probes don't read exactly the same, but I need a new backup. Would the D-D or Red Sea suffice for this? I also use it for mixing salt water.

Those are very good.

 

[mrjlopez731]

Thanks for posting this forum, it's was helpful and will be taken as a positive and useful tool to have. I see the discussion is still ongoing but this has given me more insight on this topic.