Its because the metal "well" is well, metal, and cold. It doesn't matter though as it has automatic temp compensation. Just make sure the temp is solid(not rising or lowering) before taking a reading.Well I bought this a week ago because I started doing my own water changes with rodi water and salt
Digital Seawater Refractometer MA887 - Milwaukee
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The specific gravity is great, but the temp on it, isn't accurate! Anyone else have this problem? If the room is 74 degrees, the instrument says about 72 degrees because the metal cylinder makes it cold..... add a sample water dot and it barely moves the temp to 72.4 or 72.6 etc... even warm water in the 80s doesn't even reflect it on the refractometer..... i huff some hot breath on the metal to w arm it up, but then its just as inaccurate the other way. i contacted milwaukee for answers why it even shows temp when it is not accurate
Also do not 0 out the meter with RO/DI. It will throw it off. It has to be zeroed with steam distilled. If you run out, just email Milwaukee and they will send you more.