Calibrating Refractometer

[tqreefrookie]

The directions says to calibrate the refractor with distill water. Can I calibrate it with RO water and it will be just as accurate?

 

[sjm817]

No. You need to calibrate it with a 35 ppt salinity solution.

 

[tqreefrookie]

sjm817,
Where would I get 35 ppt salinity solution? The kit doesn't come with any calibrating solution

 

[sjm817]

you can use this

 

[OranguTang]

Why can't you use RO and calibrate to 0ppt?

 

[sjm817]

Refractometers and Salinity Measurement

 

[OranguTang]

Thanks

 

[Tennsquire]

You can use this recipe in a pinch to make a calibration solution:

http://www.reefkeeping.com/issues/2004-06/rhf/index.php

 

[Racing1]

You can calibrate using pure water or 35ppt water soultion....

Read the article and it purely states that either method is accetable.....

 

[sjm817]

Pure water is not acceptable unless you are testing fresh water. It has been shown many times over that some -not all- refractometers are off by .002 - .004 when calibrated with RO/DI at SW levels.

Refractometers are a quick and often accurate way to measure the salinity of reef aquarium water. Once checked to be sure that they were made correctly, they may provide years of service, providing they are not dropped onto a hard surface or into an aquarium. As with many devices, however, you sometimes get what you pay for, and sometimes less. Very inexpensive refractometers can be prone to errors and may need to be checked in a solution matching seawater, not just pure freshwater.

These are the blue ATC models that many people buy and are not accurate when calibrated with fresh water. A better brand may be. You always calibrate any measuring device to a standard that you want to measure. You want the refractometer accurate @ 35ppt, not 0.

 

[Jefe12234]

I have one of the blue ATC refractometers that I calibrated to RO/DI water. When I recently bought a calibration solution to test it, I found it was off by 3ppt. The calibration solutions are only a few dollars, get one.

 

[sjm817]

Yeah. That is typical. The blue ATC (I have one) off by .003.