Patent ID: 8571817

Claim:
An apparatus comprising: a flow controller to control gas flow through a bubbler, the flow controller providing a plurality of flow measurements at first and second instants; a pressure controller to measure pressure in the bubbler, the pressure controller providing a plurality of pressure measurements corresponding to the plurality of flow measurements at the first and second instants; and a control processor coupled to the flow controller and the pressure controller to determine amount of precursor chemical in the bubbler based on volume consumed between first and second instants using the plurality of flow measurements and the corresponding plurality of pressure measurements, wherein the control processor comprises: a pressurization rate processor to calculate first and second pressurization rate curves at the first and second time instants, wherein the pressurization rate processor comprises: a flow interface coupled to the flow controller to provide flow set points and obtain flow measurements for predetermined flow values in the plurality of flow measurements, a pressure interface coupled to the pressure controller to provide pressure set points and obtain pressure and time measurements at the predetermined flow values, and a rate calculator coupled to the flow interfaces to calculate first and second pressurization rates at the predetermined flow values at the first and second time instants using the pressure and time measurements, the first and second pressurization rates forming the first and second pressurization rate curves, respectively, and a volume calculator coupled to the pressurization rate processor to compute the consumed volume based on first and second volumes at the respective first and second time instants, the first and second volumes being computed using slopes of lines fitting the first and second pressurization rate curves.