Products frequently need to be evaluated for correct flow rate to ensure the passage of air through devices being tested. Unsophisticated leak test machines are unable to measure a true gas flow rate. Some testers use pressure differential to calculate an apparent flow rate. At low flow, the pressure differences are extremely small and might be subject to measurement errors if the differential transducer is not sensitive enough.

As an introduction to the technique of mass flow measurement for the detection of leaks in medical devices Uson has released an application note that describes the theory of mass flow and its practical application for the detection of leaks and verification of flow rate in medical devices. Uson mass flow testers use a micro-machined solid-state mass flow transducer to measure the actual flow through the test product. Full details of the test and a circuit diagram are provided in the application note Mass Flow Theory AN-8 which may be downloaded by joining Uson's literature Club at registration is free and members gain access to all application notes, white papers and product literature.