The Pioneer of Modern Leak Testing

Differential Mass Flow Leak Test

What is a Differential Mass Flow Test?

Differential Mass Flow gets its name from how the flow meter is connected in the circuit. Unlike most of our mass flow applications where one side of the flowmeter is connected to the pressure regulator for the entire cycle in differential pressure, the differential mass flow circuit the flow sensor’s input is connected to a reference volume and the outlet is connected to the test part. Thus, it gives the appearance of a differential pressure leak test but instead of a differential pressure sensor, there is a mass flow sensor. Rule of thumb is for the small flow rates, the reference volume should be significantly larger than the part volume. Remember this rule because if the reference and part volumes are equal, only half of the leak rate will be measured by the flowmeter.

How is a Differential Mass Flow Test Performed?

The part is pressurized with a bypass circuit and a majority of air flows through the bypass to the test part. Next, the bypass is closed, and all the flow is directed through the mass flow sensor.

The reference tank is now making up any loss of air through the part. At this point, the tester can be calibrated with standards comp and cal, or the sensor can be read directly.

Differential Mass Flow Test Pneumatic Diagram
Differential Mass Flow Test Pneumatic Diagram

Which Uson leak testers perform Differential Mass Flow leak tests?

Optima vT – A versatile and customizable leak tester with up to two channels and eight sensor inputs that supports pressure decay, differential pressure, mass flow and other common tests

Qualitek – Fast, sensitive and accurate pressure decay, differential pressure and mass flow leak testers

Sprint – Small foot print single or multi channel pressure decay and flow testers

Vector – Uson’s most powerful and configurable leak and flow tester, fully customizable pneumatics, up to ten independent test channels supporting a wide variety of input sensors

Uson Innovative Systems (UIS) – Custom made manual, semi automatic and fully automatic leak test systems and fixtures

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