Design of a pressure balance with a small and calculable change of area with pressure

The design and analysis of a pressure balance using a finite element method is described. The design precisely defines the pressure gradient in the ga p and provides isolation from end-mounting effects. It also simplifies the finite element analysis. The change of area with pressure is calculated for four different operating modes, along with the gap profiles and pressure g radients. The sensitivity of the change in area with pressure to the piston -cylinder geometry, materials and fluid is analysed. The results indicate t hat the simple mode of operation (no external jacket pressure) is preferred as it produces a small uncertainty in the change of area with pressure and is easy to implement.