Refractometer calibration suggestions please?

u1tranova · Feb 15, 2012

I just got my refractometer in today and I am unsure as to how I should calibrate. There are so many opinions, its hard to decide which way I should do this. The instructions say to use distilled water. I would like to start mixing saltwater today, but all I have is rodi on hand and no calibration fluid. Would rodi water be ok to calibrate it? Any help would be appreciated. Thanks

kuyatwo · Feb 15, 2012

Call your lfs see if they can calibrate it for you if they have the calibration solution. You really are not suppose to use ro/di water to calibrate your refractometer

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pickupman66 · Feb 15, 2012

Ive used RO/Di on mine with good success. Ro/Di is better than distilled...

revhtree · Feb 15, 2012

I also use RO/DI.

kschweer · Feb 15, 2012

I use RO/DI as well. Someone on the forum has posted in the past about making his own calibration fluid. I can't remember the recipe (amount of salt to water) but I'll look around for it.

Dave3112 · Feb 15, 2012

I have used both RO/DI and calibration fluid and both are good ways to do it. RO/DI will read 0ppm and the cal. fluid is 35ppm. I believe.

Dowtish · Feb 15, 2012

If your refractometer says to use RODI, then go ahead, should be okay. But the only part of the argument that makes sense to me to actually use calibration fluid, is the fact that it calibrates the instrument to the actual level you are using it for. You will never be checking for zero on your refractometer. And just like calibrating anything else, the point is getting it close to what you need it for, not the lowest possible end of the instrument. Like calibrating my ph meter, you use a 7.01 fluid, and then a 10.0 fluid. so you can get hopefully right in the middle.

Dave3112 · Feb 15, 2012

Dowtish said:
If your refractometer says to use RODI, then go ahead, should be okay. But the only part of the argument that makes sense to me to actually use calibration fluid, is the fact that it calibrates the instrument to the actual level you are using it for. You will never be checking for zero on your refractometer. And just like calibrating anything else, the point is getting it close to what you need it for, not the lowest possible end of the instrument. Like calibrating my ph meter, you use a 7.01 fluid, and then a 10.0 fluid. so you can get hopefully right in the middle.

Great point, Chris.

u1tranova · Feb 15, 2012

Chris at AC helped me out. We calibrated using RODI and it matched up with his. So its reading correctly right now. Im thinking of trying the calibration fluid also. Any links to buy some or does anyone in the club have any to spare?

Dowtish · Feb 15, 2012

This is the stuff I use.

Aqua Craft Refractometer Calibration Fluid - English

Bishop · Feb 15, 2012

I use tap water. I'd certainly trust RO/DI for calibration. Sure, using a 35ppm solution is better but if it reads a 35ppm solution as 35ppm and it reads 0ppm water as anything other than 0ppm, it is not out of calibration. That would be a faulty refractometer.

andywe · Feb 15, 2012

My Refrac is is made to be calibrated with RODI, however I do use both. I use RO/DI most the time and every so often check with the calibration fluid. If you buy calibration fluid, make sure it is for use on refractometers. Many salinity calibration fluids are for probes and are chemically accurate, but not accurate for fractal use.

Also, make are your refract is an ATC type (auto temp adjusting), otherwise you will need to ensure you measure quickly and account for temp variance.