Atec Flexim-F610 - Manual (Page 3)

TSFLUXUS_F601V1-5-1US_Lus, 2014-02-25 3
Technical Specification FLUXUS® F601
Function
Measurement Principle
Transit Time Difference Principle
In order to measure the flow of a medium in a pipe, ultrasonic signals are used, employing the transit time dif-
ference principle. Ultrasonic signals are emitted by a transducer installed on the pipe and received by a sec-
ond transducer. These signals are emitted alternately in the flow direction and against it.
As the medium in which the signals propagate is flowing, the transit time of the ultrasonic signals in the flow
direction is shorter than against the flow direction.
The transit time difference, ∆t, is measured and allows the flowmeter to determine the average flow velocity
along the propagation path of the ultrasonic signals. A flow profile correction is then performed in order to ob-
tain the area averaged flow velocity, which is proportional to the volumetric flow rate.
Two integrated microprocessors control the entire measuring process. This allows the flowmeter to remove
disturbance signals, and to check each received ultrasonic wave for its validity which reduces noise.
HybridTrek
If the gaseous or solid content in the medium increases occasionally during measurement, a measurement
with the transit time difference principle is no longer possible. NoiseTrek mode will then be selected by the
flowmeter. This measurement method allows the flowmeter to achieve a stable measurement even with high
gaseous or solid content.
The transmitter can switch automatically between transit time and NoiseTrek mode without any changes to
the measurement setup.
Calculation of Volumetric Flow Rate
= k
Re
.
A
.
k
a
.
∆t/(2
.
t
fl
)
where
Path of the ultrasonic signal Transit time difference ∆t
= volumetric flow rate
k
Re
= fluid mechanics calibration factor
A = cross-sectional pipe area
k
a
= acoustical calibration factor
∆t = transit time difference
t
fl
= transit time in the medium
t
0
t
1
t
2
V·
V·