Differentiation Factor

The differentiation factor (DF) is a dimensionless measurement value which can be used to identify the liquid flowing through the pipe.
Before SW version A.05.00.00, differentiation factor was named density factor. Given the fact that the option density appeared, the name was changed in order to avoid confusion.
The DF is a non-calibrated acoustic measurement based on the measurement of the speed of sound in the liquid and can be compensated by temperature. The DF gives an idea of the density of most of aqueous liquids. By default, the temperature compensation is related to water.
Air bubbles in the liquid have an unwanted effect on the DF accuracy.
The device measures DFs in the range of 0.8...1.3.
  • If a liquid flowing through the pipe has a higher density than water, the measured DF is higher than 1.
  • If a liquid flowing through the pipe has a lower density than water, the measured DF is lower than 1.
Examples of DF ranges:
  • The DF of water is in the range of 0.95...1.05.
  • The DF of tomato ketchup is in the range of 1.1...1.3.
You can set the 6 constants (a0...a5) of the equation which compensates the temperature of the liquid to calculate the DF:
a0 + a1T + a2T
2
 + a3T
3
 + a4T
4
 + a5T
5

Damping

The damping makes it possible to damp the fluctuations of the measured values of the differentiation factor (DF):
  • on the display,
  • on the totalizers,
  • on the PLC input.
The damping set for an analog output comes in addition to the damping of the DF.
The damping is not applied to the new measured value if the 2 following conditions are met:
  • a Low, Medium or High damping level is active,
  • and the variation between 2 values that are measured one after the other is higher than 30 % (for example when changing the liquid in the pipe).
By default, the DF values are damped with the level None.
The Low damping level or no damping at all (None) are suited for applications/processes that need fast response times.
The Medium damping level or the High damping level are suited if the DF values change slowly.
Differentiation factor damping level selections
Damping level
Response time
None
0 s
Low
1 s
Medium
10 s
High
30 s
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