Just got a BRS ATC refractometer today to compare it to my hanna (funny how I'm using a 30 dollar instrument to test the accuracy of an 80 dollar one ). Thing is, when calibrating (using calibration fluid) I cant seem to move the line above 30/31 (I'm trying to get it to 35 per the instructions). It goes below that number just fine but won't budge past it. I can still keep twisting the calibrator past it but it remains still. What am I doing wrong?