Acoustic Transmission Factor

The acoustic transmission factor makes it possible to know the quality of the transmission of sound in the liquid thus the reliability of the measurements.
Indeed, the wave transit time in the liquid and the wave amplitude change depending on the following criteria:
  • the type of liquid: aqueous solution, oil solution, emulsion, …
  • the presence of gas bubbles,
  • the presence of solid particles,
  • the liquid temperature,
  • the DN of the pipe.
The acoustic transmission factor, given in %, is calculated on the base of the amplitude changes of the waves. The acoustic transmission factor of water without gas bubbles is equal to 100 % at a water tem­perature of +23 °C.
The temperature changes of the liquid are not compensated for the measurement of the acoustic trans­mission factor.
The device measures acoustic transmission factors from 10 % and up.
If the wave amplitude in a liquid flowing through the pipe is higher than the wave amplitude in water, the measured acoustic transmission factor will be higher than 100 %.
If the wave amplitude in a liquid flowing through the pipe is lower than the wave amplitude in water, the measured acoustic transmission factor will be lower than 100 %.
Gas bubbles or solid particles in the liquid have a similar effect on the transmission acoustic factor. If the concentration of gas bubbles or solid particles increases in a liquid, the acoustic transmission factor decreases. So, measuring and monitoring the acoustic transmission factor can be used to detect the presence of gas bubbles or solid particles in the liquid.
Take into account that special process conditions can have an effect on aging of the sensor thus on the acoustic transmission factor value.

Damping

The damping makes it possible to damp the fluctuations of the measured values of the acoustic transmission factor:
  • on the display,
  • on the totalizers,
  • on the outputs.
The damping set for an analog output comes in addition to the damping of the acoustic transmission factor.
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 %
By default, the values of the acoustic transmission factor 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 values of the acoustic transmission factor change slowly.
Acoustic transmission factor damping level selections
Damping level
Response time
None
0 s
Low
1 s
Medium
10 s
High
30 s
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