Elastic distortions of a multi‐mode piston‐cylinder unit up to 28 MPa

The elastic distortions of a special hydraulic piston gauge (PG27) operating to 28 MPa in the simple, re‐entrant and controlled‐clearance configurations were calculated by application of an anlytical iterative technique. With these calculations one can determine the radial displacements of the piston and the cylinder at any pressure and with different fluids, the pressure distribution in the clearance, and the pressure distortion coefficient of the piston‐cylinder unit under conditions of use. The effective areas based on the calculated value of the pressure distortion coefficient in each of the three configurations show agreement with the experimentally determined effective areas well inside 11 parts per million (ppm).