Calibration of high-capacity scales using hydraulics instead of weights: Metrological traceability and measurement uncertainty

The calibration of non-automatic weighing instruments with a capacity of several tons, such as processing tanks, requires significant efforts and poses safety risks to calibration technicians. In response to these challenges, METTLER TOLEDO has developed a calibration method utilizing hydraulic actuators and force measurements, which has achieved ISO 17025 accreditation in several countries. This article outlines how hydraulic calibration can be aligned with traditional calibration standards, such as EURAMET Calibration Guide 18, and how traceability to the SI unit of mass can be ensured. An approach for calculating measurement uncertainty at calibration is discussed. Calibration results demonstrate high agreement between traditional calibration with test weights and the new hydraulic force calibration.