A dependent closed pressure vessel is fluidly coupled to an independent closed pressure vessel. A pressure sensor monitors pressure in the vessels to generate raw pressure measurement data. A flow meter monitors multidirectional rate of flow of fluid between the vessels and the volume of fluid flowing from the independent closed pressure vessel to generate raw rate of flow and raw volume measurement data. A pressure/flow regulator valve adjusts pressure in the dependent closed pressure vessel in response to a pressure set point signal generated in response to the raw pressure data, adjusts the rate of flow of fluid between the vessels in response to a rate of flow set point signal generated in response to the raw rate of flow data, and adjusts the rate of flow of fluid between the vessels in response to a volume set point signal generated in response to the raw volume data.