Abstract: A pressure controller rapidly, precisely sets and stabilizes the pressure in a test volume to a target pressure by opening a fast inlet solenoid valve or a fast outlet solenoid valve, and opening a slow inlet solenoid valve or a slow outlet solenoid valve, to rapidly increase or decrease pressure in the manifold. When the pressure has reached a predetermined level, the fast inlet or fast outlet solenoid valve is closed. Then only the slow inlet or slow outlet solenoid valve remains opened to further increase or decrease the pressure to a second predetermined level. Then, based on the present pressure in the manifold and the test volume, a computation is made of the amount of gas needed to be injected into the manifold to increase the pressure to the target pressure. A computation is made of the time duration during which the slow inlet valve and the slow outlet valve must be differentially opened to increase the net amount of gas injected into the manifold and test volume by the computed amount.