Help calibrate refractometers



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Jan 28, 2020
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Los Angeles
Ok so I have a Milwaukee refractometer, a Hanna electronic salinity meter, two regular refractometers, and a apex with salinity probe.

I have three different calibration fluids: 35ppt that came with Hanna. A BRS bottle of 1.025 ppt and another bottle of 1.025.

I have tried to calibrate all 5 devices and all get different readings. Between 1.022 and 1.026. I now have no idea which one is closest to correct and can’t seem to get any of them to be consistent.

is there a reliable calibration fluid I can trust? Or how can I know for sure which is correct?

side note- can Milwaukee be zeroed with rodi? Or does it have to be distilled water? I tent to Trust the Milwaukee the most but now I’m questioning my self.

is this common or am I just making this a bigger deal then it really is lol.
Aquarium Specialty - dry goods & marine livestock


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Aug 18, 2016
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I tried all brands of standards and got different results on all of them. I have 3 refractometers and a conductivity meter. I used Randy's diy standard (different formula for the type of meter) and got much better readings. Then I found accurasea natural seawater standard and it works for all the types of meters!!! Works great and guess what? Randy's DIY matches it exactly. So I'm sticking with it.

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