FEA calculation of pressure distortion coefficients of gas-operated pressure balances – EURAMET project 1039

Abstract Finite element analysis methods were developed and applied to gas piston–cylinder units (PCUs) of piston- and cylinder-floating configuration (2, 5, 10 and 20) cm 2 nominal effective area, operated in gauge and absolute mode at pressures (0.06–7.5) MPa to determine their zero pressure and pressure-dependent effective areas, as well as pressure distortion coefficients ( λ ) with associated uncertainties. Real dimensional properties of the PCUs were used. λ were found to be independent of gas (ideal, N 2 , He) within the viscous flow model, but strongly dependent on the gap shape, operation mode and elastic properties. Results demonstrate good agreement for λ , with its uncertainty for different PCUs varying between (0.03 and 0.21) × 10 −6  MPa −1 corresponding to maximum relative uncertainties in pressure of (0.07–0.34) × 10 −6 .