Functional Description; Ultrasound Combined With Piezo Ceramics; Principles; Transient Time Method - Kamstrup ULTRAFLOW 54 Technical Description

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TECHNICAL DESCRIPTION ULTRAFLOW 54 and 34

8 Functional description

8.1 Ultrasound combined with piezo ceramics

Flow sensor manufacturers have been working on alternative techniques to replace the mechanical principle.
Research and development at Kamstrup has proved that ultrasonic measuring is the most viable solution.
Combined with microprocessor technology and piezo ceramics, ultrasonic measuring is not only accurate but also
reliable.

8.2 Principles

The thickness of a piezo ceramic element changes when exposed to an electric field (voltage). When the element
is influenced mechanically, a corresponding electric charge is generated. In this way the piezo ceramic element
can function either as a sender or a receiver or both.
Within ultrasonic flow measuring there are two main principles: the transit time method and the Doppler method.
The Doppler method is based on the frequency shifting which is generated when sound is reflected by a moving
particle. This is very similar to the effect you experience when a car drives by. The sound (the frequency) decreases
when the car passes by.

8.3 Transient time method

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The transient time method used in ULTRAFLOW utilizes the fact that it takes an ultrasonic signal emitted in the
opposite direction of the flow longer time to travel from sender to receiver than a signal sent in the same direction
as the flow.
The transient time difference of a flow sensor is very small (nanoseconds). Therefore, the time difference is
measured as a phase difference between the two 1 MHz sound signals to obtain the necessary accuracy.
PHASE DIFFERENCE
T
Against the flow
With the flow
t
Diagram 8
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5512-385 GB/02.2014/Rev. H1