Abstract: A method dispenses and/or aspirates a predetermined volume of fluid from a chamber. The chamber includes a lower portion containing fluid and an upper portion containing gas. The method includes measuring an initial pressure in the upper portion and introducing or evacuating a known quantity of gas into or out of the upper portion. The volume of gas in the upper portion is determined based on the volume of gas introduced or evacuated from the upper portion and a measured change in pressure in the upper portion. An upper portion target pressure that will dispense or aspirate a predetermined volume of fluid is determined. A controllable valve is opened while the pressure in the upper portion of the chamber is monitored. Once the target pressure is reached, the predetermined volume of fluid has been dispensed or aspirated, and the controllable valve is then closed.

Abstract: An apparatus and method for precisely dispensing liquid fluid from a container are disclosed. The apparatus comprises a metering unit having a gas feedthrough channel with a first end extending in a gas containing part of the chamber and a second end opposite the first end extending outside the chamber, the metering unit further comprising a flow sensing assembly configured to measure a gas pressure differential ?p and/or gas flow V{dot over ( )} within the gas feedthrough channel and to introduce or release a determined volume of gas in the chamber to dispense a controlled volume of liquid from the chamber.

Abstract: An apparatus dispenses and/or aspirates a predetermined volume of fluid from a chamber. The chamber includes a lower portion for containing fluid and an upper portion for containing gas. The apparatus includes a controllable valve arranged to be in fluid communication with the lower portion of the chamber, a pressure sensor arranged to be in fluid communication with the upper portion of the chamber, a pump configured to be in fluid communication between a source of gas and the upper portion of the chamber, and a controller in operative connection with the controllable valve, the pressure sensor, and the pump. The controller is configured to receive signals from the pressure sensor and to control operation of the pump and operation of the controllable valve based on said signals from the pressure sensor. A method for dispensing and/or aspirating a predetermined volume of fluid utilizes this apparatus.