DURAG D-FL 200 - (Fig. 1) Measuring Principle

D-FL 200 / Rev. 6 2
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Industrie Elektronik GmbH & Co KG
v Gas velocity
L Measuring path in the medium
α Angle of installation
(Fig. 1) Measuring principle
The two equations shown before for impulse transit times may be reduced down for sonic velocity ‘c’
and gas velocity ‘v’:
c
L
2
tt
tt
=⋅
+
⋅
−+
−+
Equation 3
v
L
2cos
tt
tt
=
⋅
⋅
+
⋅
−+
−+
α
Equation 4
The speed of the sound changes with the temperature of the gas according to the next formula.
whereby T is in Kelvin. With this equation the gas temperature can be obtained from the measurement.
K
T
273s
m
331,6 c
⋅=
Gl.5