Method for correcting for changes in air pressure above a liquid to be dispensed from a container mounted on a probe

摘要

There is disclosed dispensing apparatus using a container for liquid, the apparatus comprising pressurizing means for aspirating liquid into the container, and for pressurizing liquid within the container to dispense the liquid. To control the ambient pressure of the atmosphere above the liquid within the container, system control means and a method of control are provided. Such means and the corresponding step of the method comprise (a) means for repeatedly sensing the air pressure above the level of the liquid within such container, and for repeatedly generating a signal corresponding to said pressure; (b) means for reading and storing the signal when it represents a desired baseline air pressure; (c) means for storing a tolerance factor; (d) means for determining the difference between the signal stored by means (b) and the signal repeatedly generated by the sensing means, as a difference value; and (e) actuating means for activating the pressurizing means to produce a negative or positive pressure differential when the determining means (d) detects that the absolute value of the difference value is greater than the value of the stored tolerance factor.