Refractometer Suggestions?

[WABlonde]

We were talking last night of picking up a refractometer for hyposalinity treatment. Google just brings up too much of something I know nothing about. Do you have any suggestions for a fairly decent refractometer that won't kill my checking account? Would also be nice to know best place to pick one up.

Thanks much

 

[jrgilles]

sent you a pm

 

[NWDiver]

Having purchased a "cost-effective" model the first time around and having no end of trouble with it, I asked Boomer for his suggestion. He likes this one Refractometers
I have used it for several months and I've been very happy with it.

-Todd

 

[J-Ranko]

I don't have any specific brand's to recommend, but I do have a suggestion about calibration. This is important if you're aiming to accurately manipulate your salinity with the typical refractometers available for this hobby.

Most hobby grade refractometers are actually brine (not seawater) refractometers. Because of this, a lot of users who calibrate their refractometers with distilled or RO/DI water to zero will get a higher reading than is actually the case. This results in a salinity that is lower than they think they have. More specifically, about 1.7 ppt lower.

To correct for this, if you calibrate to zero with distilled, aim for a reading that is 1.7ppt higher than what you actually want. So if you're targeting a salinity of 35ppt, add salt until you get 36.7 ppt on the refractometer. You can also calibrate the refractometer to 35ppt with a calibration solution that has a refractive index of 1.3394.

Of course you can also just buy a true seawater refractometer. But those don't come cheap.

 

[pblutang]

I have a brand new vertex refractometer FS if interested. Here is a link to my post.
http://http://www.reeffrontiers.com/forums/f10/fs-ft-vertex-refractometer-58457/

 

[Frankie]

Milwaukee Refractometer with ATC

Best one I have used yet.

 

[WABlonde]

I have a brand new vertex refractometer FS if interested. Here is a link to my post.
http://http://www.reeffrontiers.com/forums/f10/fs-ft-vertex-refractometer-58457/

Thanks for forwarding link. I'll talk to the bf about it as well as do some more research. Wouldn't be able to pick up it 'til Friday (payday).

 

[DonW]

I don't have any specific brand's to recommend, but I do have a suggestion about calibration. This is important if you're aiming to accurately manipulate your salinity with the typical refractometers available for this hobby.

Most hobby grade refractometers are actually brine (not seawater) refractometers. Because of this, a lot of users who calibrate their refractometers with distilled or RO/DI water to zero will get a higher reading than is actually the case. This results in a salinity that is lower than they think they have. More specifically, about 1.7 ppt lower.

To correct for this, if you calibrate to zero with distilled, aim for a reading that is 1.7ppt higher than what you actually want. So if you're targeting a salinity of 35ppt, add salt until you get 36.7 ppt on the refractometer. You can also calibrate the refractometer to 35ppt with a calibration solution that has a refractive index of 1.3394.

Of course you can also just buy a true seawater refractometer. But those don't come cheap.

Almost all refractometers sold today in the reef / SW industry are calibrated to sea water. IIRC they should be recalibrated for hyposalinity 2 pts 35 ppt 1 pt fresh water.

Don

 

[J-Ranko]

Almost all refractometers sold today in the reef / SW industry are calibrated to sea water. IIRC they should be recalibrated for hyposalinity 2 pts 35 ppt 1 pt fresh water.

Don

I don't understand what you mean. There's a difference in the refractive index of seawater vs. saltwater (brine). It's not simply a matter of calibration. Calibrating a refractometer is merely adjusting it so that it reads a standard solution correctly. But that's a different issue from the refractive index of seawater vs. saltwater. A 35 ppt sodium chloride solution has the same refractive index as a 33.3 ppt seawater solution. The reason I brought this up is that most refractometers sold today in the reef industry are brine (sodium chloride) refractometers, not seawater refractometers.

Granted, the differences in refractive index are small enough that they are not fatal, and can be easily corrected for with proper calibration. Now one can assume that the refractometer is calibrated to seawater out of the box, but that's not a very good practice. And besides, it's easy enough to fix this by simply calibrating the refractometer (whether brine or true seawater) to a standard solution with a refractive index of 1.3394.

See Randy's RK article "Refractometers and Salinity Measurements" here.

 

[J-Ranko]

This might come in handy when selecting a refractometer to buy.

According to Boomer, the few true seawater refractometers available are:

Hand-Held
The Vee-Gee refract sold by The Filter Guys, the Vital Sine from Foster & Smith, ATAGO, and D-D

Digital
Misco (famous for its Digital seawater refract), Hanna Digital seawater refract (and renamed Hanna, Milwaukee)

 

[DonW]

I don't understand what you mean. There's a difference in the refractive index of seawater vs. saltwater (brine). It's not simply a matter of calibration. Calibrating a refractometer is merely adjusting it so that it reads a standard solution correctly. But that's a different issue from the refractive index of seawater vs. saltwater. A 35 ppt sodium chloride solution has the same refractive index as a 33.3 ppt seawater solution. The reason I brought this up is that most refractometers sold today in the reef industry are brine (sodium chloride) refractometers, not seawater refractometers.

Granted, the differences in refractive index are small enough that they are not fatal, and can be easily corrected for with proper calibration. Now one can assume that the refractometer is calibrated to seawater out of the box, but that's not a very good practice. And besides, it's easy enough to fix this by simply calibrating the refractometer (whether brine or true seawater) to a standard solution with a refractive index of 1.3394.

See Randy's RK article "Refractometers and Salinity Measurements" here.

I guess I didnt word that properly. Almost every refract sold in this hobby are made by Sybon, it doesnt matter who's name is on it. Calibrate it with 35ppt SW or 53 cal fluid either way its going to be on the money no adjustment or offset is needed. You do have to offset the reading when using pure water to calibrate. It should read in the red when testing pure water and calibrated with 35ppt solution. There was a bunch of talk about this a few years ago. Something about someone saying you couldn't use 53 solution without adjusting and american marine disproving that at least with their refracts which are just Sybon and the most widely sold and rebranded refracts.
For hypo salinity with these refracts you can make your own solution. You recal with your own solution because as you go down the scale the refract will be a tad off if you did the cal at 35 ppt or 53 ms.

Don

 

[J-Ranko]

I guess I didnt word that properly. Almost every refract sold in this hobby are made by Sybon, it doesnt matter who's name is on it. Calibrate it with 35ppt SW or 53 cal fluid either way its going to be on the money no adjustment or offset is needed. You do have to offset the reading when using pure water to calibrate. It should read in the red when testing pure water and calibrated with 35ppt solution. There was a bunch of talk about this a few years ago. Something about someone saying you couldn't use 53 solution without adjusting and american marine disproving that at least with their refracts which are just Sybon and the most widely sold and rebranded refracts.
For hypo salinity with these refracts you can make your own solution. You recal with your own solution because as you go down the scale the refract will be a tad off if you did the cal at 35 ppt or 53 ms.

Don

Oh, OK. I agree with you then. Thanks for the clarification.