A manometer with an effective piston area unchanged by pressure

High-Pressure Calibration: A Critical Review

“…The distortion of the simple gage even at pressures below 300 bars was shown to be linear, and the measured distortion coefficient A indicated a pressure' gradient near the upper portion of the piston. Zhokhovskii (1959aZhokhovskii ( , 1959bZhokhovskii ( , 1960Zhokhovskii ( , 1964 has carried out a rather straightforward but thorough analysis based on the assumption that the change in radius a of the piston and radius b of the cylinder at a general position x, along the length of the piston could be evaluated using the Lame ·equations in terms of the }ll'eS<;;;llre in the rrpviC'e ::1t the point y Since the Lame equations apply rigorously only to long rods and hollow cylinders where the pressures are uniform along the length, one would expect serious discrepancies if the pressure variation along the piston length were abrupt, but the assumption would be more satisfactory if the pressure gradients were small and appeared over a large portion of the crevice length. Zhokhovskii's analysis makes no other assumption as to the functional variation along the length of the crevice but does assume perfectly cylindrical geometry and that no other deformation takes place except that described above by the Lame equation.…”