Patent ID: 7757554

Claim:
A mass flow verifier for verifying flow measurement of a fluid by a fluid delivery device, the mass flow verifier comprising: a chamber defining a plurality N of inlets, the chamber configured to receive at each of the inlets a flow of the fluid from the device; a pressure sensor configured to measure pressure of the fluid within the chamber; a plurality N of critical flow nozzles, each critical flow nozzle located adjacent to a corresponding one of the inlets, each critical flow nozzle located upstream of the chamber along a flow path of the fluid from the device to the chamber through the corresponding inlet; wherein for all i (i=1, . . . , N), the i-th critical flow nozzle is configured to maintain, during a critical flow time period t cf,i (i=1, . . . , N) for the i-th critical flow nozzle, the flow rate of the fluid through the i-th critical flow nozzle substantially constant and substantially insensitive to variation in pressure within the chamber.