Here is my issue:
I have a Vegapuls SR68 in order to measure level in a storage tank (some with gasoline and other Diesel), capacity 100,000 bbls. The calibration was done (without product). Later the tanks were filled and the measured values were different. Then the instruments were recalibrated getting the right values, but at the next day appeared decalibrated. The instrument get a better behaviour when was changed the medium (Medium setup/liquid @ bulk solid) to solid, but the problem still persist. the instrument measured in meters.
Thanks for your time