Warren if i am not mistaken you use RO/DI to get it to the bottom reading ie 0. May be wrong here as i have never done it.
Guys I only have a reading of 1 as the lowest. Is this a mistake on your part or does my Refractometer have a digit missing ?Warr, you take a few drops of RO/DI and put it on the prism - no salt - close and look into it. Adjust it till back at 0 (small screw on top). Suck up tank water and test - accurate reading.
I calibrate mine everytime before I measure my tank and the make-up water - just to be safe. I rinse the prism with the new water to be tested by holding the refractometer with the prism facing down and slow squirt water over prism and tilting glass - just to get rid of dust and/or drops from "other" water and so my readings aren't affected. I sometimes calibrate, test tank water and then make-up water all after each other.
That sounds like what I was originally told. But what is the measurements of the mixture that needs to be made up?Calibration so that RO or RO/DI or distilled water = 0 is one way to calibrate but not the best because the refractometer could still be a bit out if say 1ppm shows as 1.1ppm, by the time you're looking at 35 ppm it will show as 38.5ppm. The better way to calibrate is using a sample with a known ppm around the range you would usually be testing at, ie 35 or so. This is why the "experts" calibrate with a mixture of known quantities rather than at 0.
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