Patent ID: 8382444

Claim:
A method for controlling fluid pressure in a multi-stage pump comprising: accessing a baseline profile for a known good dispense cycle, wherein the baseline profile provides a profile of an operating parameter of the multi-stage pump; operating a feed pump, a dispense pump and a set of valves to perform a new dispense cycle including multiple segments; continually determining values of the operating parameter during the new dispense cycle; creating a first operating profile for the operating parameter using the values of the operating parameter; comparing the first operating profile with the baseline profile to confirm that the new dispense cycle resulted in a good dispense; and if a good dispense did not occur, performing one or more of sending an alarm and changing the operation of the multi-stage pump; wherein operating the feed pump, dispense pump and set of valves to perform the new dispense cycle comprises: operating the feed pump to reduce a volume of a feed chamber at a first predetermined rate; opening a barrier valve to allow a fluid in the feed chamber to enter a dispense chamber while keeping an outlet valve closed so that none of the fluid entering the dispense chamber is dispensed; taking pressure measurements of the fluid using a pressure sensor; determining whether a first pressure measurement is greater than a predetermined pressure; in response to the first pressure measurement being greater than said predetermined pressure, operating the dispense pump to increase a volume of the dispense chamber at a second predetermined rate; taking a second pressure measurement while the dispense pump is operating to increase the volume of the dispense chamber; determining whether the second pressure measurement is greater than a first threshold or less than a second threshold; in response to determining that the second pressure measurement is greater than the first threshold, operating the feed pump at a decreased speed; in response to determining that the second pressure measurement is less than the second threshold, operating the feed pump at an increased speed; determining whether the operation of the dispense pump has caused the volume of the dispense chamber to reach a predetermined volume; in response to determining that the volume of the dispense chamber has not reached the predetermined volume, repeating the method from the step of measuring the second pressure; and in response to determining that the volume of the dispense chamber has reached the predetermined volume, stopping the operation of the feed pump and the dispense pump.