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5.1.3 Principle of Operation for
Flow Measurement
The Flow is measured over a differential pressure
measurement in the flow channel. A screen is used as the
restrictor.
: dynamic viscosity of gas [Pa s]
: density of gas [kg / m3]
c1, c2: device specific constants (channel geometry)
Dynamic
Viscosity
•
The viscosity of a medium is its
resistance to shear or flow
•
The viscosity is strongly temperature
dependent
•
Small dependency on humidity and
pressure
Density
•
The density is a measure of the
medium's mass per unit of volume
•
The density is strongly temperature and
pressure dependent
The dependence on the ambient conditions is the reason
why the flow is sometimes transferred to standard
conditions (>5.2 Standard Conditions for Flow
Measurement).