How to do calibration with your GVDA GD316 GD316 New Digital Refractometer Brix Meter Fruit Juice Wine Beer Drinks Sugar Content Measuring Instrument Saccharimeter
if you need calibrate the device, proceed as below:
①Power on
②Drop about 0.3ml purified water, close the lid
③Press 
two times
④ 
twinkling
⑤Press 
⑥0.0% brix, calibration succeed
