A finite element method to evaluate the pressure distortion coefficient in pressure balances

The increasing interest in high-pressure primary standards has led in recent years to special attention to the design and metrological characterisation of pressure balances, in particular to the evaluation of the pressure distortion coefficient of piston - cylinder units. Several simplified and empirical methods are generally used to evaluate this coefficient even if most of them are not applicable to complex units. A finite element method is reported, which was developed by the University of Cassino and the Istituto di Metrologia "G Colonnetti" of Turin, to evaluate the pressure distortion coefficient of piston - cylinder units. In order to validate the proposed methodology, the numerical results obtained and those determined by means of other methods (numerical, analytical, and empirical methods) were compared for the national primary pressure standard used up to 100 MPa (IMGC-100-NNtc unit).