Abstract: A system for controlling pressure associated with a volume may comprising a pump and piston/cylinder assembly, both in fluid communication with a volume of a closed fluid system. In addition, the system may comprise an actuator operatively connected to the actuator and pump to control fluid flow and pressurization or depressurization of the volume and/or fluid flow system. The pump is activated to generate a first pressure level of the closed fluid system and when this first pressure level is reached the actuator is activated to drive the piston/cylinder assembly to reach a pressure set point from the first pressure level. The system may be used as a calibrator or a pressure controller for pressure differentials, gauge pressure or absolute pressure.