What causes a refractometer to lose calibration?


SPS Addict
I have a pretty expensive ATC refractometer and I have been having problems calibrating it correctly. I have 35ppt pinpoint calibration solution and it seems to read differently between calibrations, sometimes 2-3 ppt within 10 minutes or so. Yesterday I calibrated it at 35 and today it was down to 33, I calibrated it back to 35 and cleaned my tank for a while, and about 15 minutes later I put the calibration solution again and it was reading back down at 33. The temperature did not change at all during this time. Is my refractometer just going bad? I have no idea how these things work so I don't know what might cause one to lose calibration faster over time. Thanks!


New member
Dropping it will loosen up the calibration screw, (expert experience there :) ) likely you need a new one. Not sure if you can work it back into place but it's probably just as easy to replace.


New member
clean it with ro inbetween and use the same amount of drops every time.
I also put the drops in the same spot every time.