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4
Functional principle - Ultrasonic
flow measurement
4.1
General description
th
September, 4
2018
4 Functional principle - Ultrasonic flow measurement
Content
4.1
General description ........................................... 17
4.2
Correction of the base line ............................... 21
4.2.1
Base line correction via polynomial ........................ 22
4.2.2
Correction via a piecewise linearization ................. 24
4.3
Diagnostic function Speed of Sound ............... 24
4.3.1
Standard method of SoS calculation ...................... 24
4.3.2
SoS calculation via gas components ...................... 24
4.3.3
Extended SoS calculation ...................................... 25
4.4
Import of gas composition data ....................... 27
4.4.1
Option 4: Data input on fixed defaults .................... 27
4.4.2
Option 4: Data input on fixed defaults for air .......... 28
4.4.3
Data input via RMGBus .......................................... 30
4.4.4
Data via Modbus (USM-GT-400 is SLAVE) ........... 30
4.4.5
31
4.5
Batch mode ........................................................ 36
In this chapter, you are provided with information as to how the
ultrasonic gas meter records the data. The necessary formulas
are listed for this purpose.
Figure 4.1 shows the general working principle. Transducer TD1
and TD2 are positioned opposite to each other for the measure-
ment and form a measurement path with distance L. An
ultrasonic pulse travels along the measuring path from sensor
TD1 to transducer TD2 more quickly than the other way around.
This is caused physically by vector addition of the flow velocity to
the speed of sound, the arrow above the
of flow.
Ultrasonic Flowmeter USM GT400
4.
shows the direction
v
17
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