Make sure you calibrate at room temperatureCalibrate both with 35ppt standard
We ran an experiment at the last talk. Had everyone bring their refracs and calibration solutions. After calibrating, we switched solutions and tested using that. There were more wrongs than rights. Even the 2 Milwaukee’s were off. But off by the same amount.
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I stopped using Milwaukee after consistently showing at least 1ppt error immediately after RODI calibration.Even after Milwaukee zero out with rodi water?
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Temp matter.... each refractometer is built to yield an accuracy at specific temp range..Calibrating to 35 ppt will give you more accurate results, but only if your calibration liquid is good.
And they can easily go bad if old and not quite sealed, as they evaporate slightly.
If bad, they can be WAY off.
Thus, if you are not sure, calibrate with RODI.
You will be off by a tiny bit, depending on the quality of refractometer, but never off by an amount that causes problems.
Air temp does not matter that much. Refractometers usually have compensation for that.
Even after Milwaukee zero out with rodi water?
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I would not take any measurment using smy instrument without calibrating the instrument first.The RedSea refractometers are known to not hold calibration - it's much better glass than others but I wouldn't trust it if calibrated more than 5 min ago. Maybe it's some bad batches but I have a bad one and there was a long thread on RC about this issue when RedSea had dedicated forum. My cheap Chinese is more reliable but the scale and optics is worse.
I used RODI to calibrate my Milwaukee and used this chart to make a standard to test it out (from Milwaukee manual). Just used non-Iodized Morton’s table salt and it was spot on.
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Disagree.Temp matter.... each refractometer is built to yield an accuracy at specific temp range..
If you ask vendors they will all tell you it matter...
My 2 cents, if you want to chase down to 1ppt or leas accuracy you need to follow the rules to the letter. Once we start deviating here and there, inaccuracies start adding up..