Calibrating refractometer

Thank's RAYJAY,very good info.

 

While I don't disagree calibrating is important, I wanted to add it's not a big deal if the calibration is off 3%. The more important thing is that it is consistent. Consistency is key in this hobby.

 

I agree with that.
I am still using my swing arm hydrometers after more than 20 yrs now, and don't even own a refractometer.
I DO however, have a fisher scientific certified calibrated hydrometer with cylinder that about once a year I check my two swing arms against.

 

Yeah,I think my salinity is a little high,maybe 1.027 or 1.028 but I'm not making any adjustments till I know it's an accurate reading.

 

Got the 35% fluid today FWIW to anyone there was only .01 difference when using the 35% compared to the 0% solution.

 

Must mean .001.
If everything was exact, and assuming you have an NaCl refractometer, the difference should be .0024.
Unfortunately, refractometer accuracy limitations, and calibrating fluids that aren't exactly right on, mean you could work out with better than expected results.
Even expensive refractometers can be inaccurate, but the cheaper ones more so. Most don't specify their accuracy limitations.
Here's one expensive one that lists accuracy at +-.002 although many expensive ones are accurate to within +-.0005.
Atago Special scale Refractometer Specific Gravity of Seawater - Atago SpecialScale Digital Pocket Refractometers from Cole-Parmer Canada
Some years ago, Randy Holmes-Farley did testing on various brands of pH calibration fluids, using his expensive lab equipment to test, and found quite a variance from one to another. I suspect the calibration fluids for refractometers vary as well.
The pH test results can be seen here: A Comparison of pH Calibration Buffers by Randy Holmes-Farley - Reefkeeping.com

 

Yeah I did mean .001 difference.Since I was using a floating hydrometer and trusting my eyesight when reading it I think the accuracy of this $40 refractometer is more than likely an improvement.

 

Thanks sailorguy and rayjay,

I'm starting my own thread on my results, and of course linking this thread