Refractometers

[jeff williams]

I'm looking for a Refractometer gimmie your input on what makes one better than the other. I'm not looking for the lease expensive I want accuracy and one that is saltwater specific that holds its calibration and of course temp compensating

 

[HolisticBear]

I'm looking for a Refractometer gimmie your input on what makes one better than the other. I'm not looking for the lease expensive I want accuracy and one that is saltwater specific that holds its calibration and of course temp compensating

I'm a fan of the BRS one and dislike the Red Sea variant. In both cases, I always use calibration solution prior to use. The red sea can lose calibration in two minutes if you look at it funny. The BRS holds calibration and drifts very little if any week to week. It feels better built and it's easier for my eyes to read.

There are many reviews on BRS web site for their model, price is very reasonable.

 

[Jason mack]

I think for a more accurate Reading a hydrometer from tropic marin would be beter .. i have a refractor and have now a hydro on order

 

[jeff williams]

I'm a fan of the BRS one and dislike the Red Sea variant. In both cases, I always use calibration solution prior to use. The red sea can lose calibration in two minutes if you look at it funny. The BRS holds calibration and drifts very little if any week to week. It feels better built and it's easier for my eyes to read.

There are many reviews on BRS web site for their model, price is very reasonable.

Thanks I've never used one tell me, if I'm checking newly mixed cold saltwater does it compensate for the temp or will it have to be calibrated for the colder water

 

[Ty Hamatake]

I believe it's Vertex, but I really like the scale they use. In my opinion it's much easier to read than many others.

 

[jeff williams]

I believe it's Vertex, but I really like the scale they use. In my opinion it's much easier to read than many others.

How about quality is it a good solid piece and calibration does it stay calibrated

 

[Ty Hamatake]

How about quality is it a good solid piece and calibration does it stay calibrated

I don't know that there is one out there that I personally wouldn't calibrate everytime I use it, but I would say the quality is very high. The sight was a major high point for me. A lot of the cheaper ones are loose and need to be adjusted constantly (really not a huge deal, but can get annoying), but this one had a very firm seal and would stay put.

 

[Randy Holmes-Farley Verified Community Expert]

I'm looking for a Refractometer gimmie your input on what makes one better than the other. I'm not looking for the lease expensive I want accuracy and one that is saltwater specific that holds its calibration and of course temp compensating

If you calibrate with a seawater standard, it need not be a true seawater refractometer to be accurate, but there's certainly nothing wrong with getting one.

 

[HolisticBear]

Thanks I've never used one tell me, if I'm checking newly mixed cold saltwater does it compensate for the temp or will it have to be calibrated for the colder water

The spec sheets say they are auto temperature compensating, but I've always tested within a narrow band of temperatures. When I mix salt, I throw in both a heater + powerhead, so the temp is in the 70s when I test. They are easy to use, but I do wish a digital version or larger display was available. Calibration is as simple as putting two drops on the meter, waiting 40 seconds (temperature compensating) and ensuring it's what you expect (likely 35ppt solution).

 

[Brew12]

Thanks I've never used one tell me, if I'm checking newly mixed cold saltwater does it compensate for the temp or will it have to be calibrated for the colder water

The temperature compensation has to do with the temperature of the refractometer, not the the water. The 2 drops of water will very quickly adjust to the temperature of the refractometer so the waters starting temp doesn't matter.

 

[Randy Holmes-Farley Verified Community Expert]

In general, I wouldn't overly rely on the ATC feature, and wouldn't try to calibrate and measure at significantly different temperatures.

 

[jeff williams]

The temperature compensation has to do with the temperature of the refractometer, not the the water. The 2 drops of water will very quickly adjust to the temperature of the refractometer so the waters starting temp doesn't matter.

Thanks I was under the impression the atc was for water temp

 

[Randy Holmes-Farley Verified Community Expert]

Thanks I was under the impression the atc was for water temp

The ATC adjusts for the temp of the refractometer, and a small amount of water on the refractometer gets pretty close to the refractometer.

I show how ATC works here:

Refractometers And Salinity Measurement
http://www.reefedition.com/refractometers-salinity-measurement/

Temperature and Refractive Index: ATC

It turns out that refractive index is highly dependent on temperature. When using a refractometer that does not account for this effect, temperature changes can be a large source of errors. Most liquid materials expand slightly when heated and shrink when cooled. For a given material, light can pass through it more easily when it is expanded, so the index of refraction falls when materials are warmed. However, the magnitude of this effect is different for every material, and refractometers must somehow take this into account.

Handheld refractometers account for temperature by employing a bimetal strip inside them. This bimetal strip expands and contracts as the temperature changes. The bimetal strip is attached to the optics inside the refractometer, moving them slightly as the temperature changes. This movement is designed to exactly cancel temperature’s effects on refractive index, and generally does a very good job IF the refractometer is designed to cancel out the temperature effects of the specific material being analyzed.

Because many refractometers are designed to use aqueous (water) solutions, the bimetal strip can be designed to account for the change in refractive index of aqueous solutions with temperature, although it may not be perfect in some situations because salts and other materials in the water can change temperature’s effects on refractive index by a small extent (or possibly to a large extent for very concentrated solutions, such as 750% sugar in water, but seawater is not in that category). Other details of this compensation may cause it to be imperfect (for example, the bimetallic strip provides a linear correction while the true temperature effect may be nonlinear), but those issues are beyond the scope of this article, and in general automatic temperature compensation (ATC) is a very useful attribute for aquarists using refractometers.

 

[jason2459]

The temperature compensation has to do with the temperature of the refractometer, not the the water. The 2 drops of water will very quickly adjust to the temperature of the refractometer so the waters starting temp doesn't matter.

Quickly but not instant. I wait a short bit or watch and wait for the line to stop drifting.

 

[Brew12]

Quickly but not instant. I wait a short bit or watch and wait for the line to stop drifting.

If you are seeing the line drift odds are it is not due to the temperature. Going by the thermodynamic equation that Q=UA(deltaT) the amount of time it takes for the water to reach near equilibrium with the refractometer is seconds. There just isn't enough mass of water compared to the enthalpy and surface area.

 

[jason2459]

If you are seeing the line drift odds are it is not due to the temperature. Going by the thermodynamic equation that Q=UA(deltaT) the amount of time it takes for the water to reach near equilibrium with the refractometer is seconds. There just isn't enough mass of water compared to the enthalpy and surface area.

Yes, in a mater of a few seconds you can see it drift. That is not instant.