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

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) cm2 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, N2, 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.

► Finite element analysis methods applied to gas piston–cylinder units operated in gauge and absolute mode.
► Zero pressure and pressure-dependent effective areas, distortion coefficients and their uncertainties determined.
► Real dimensional properties of piston–cylinders used.
► Distortion coefficients are independent of gas, but strongly depend on gap shape, operation mode and elastic properties.