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The temporal correlation of the actual gas composition (using the SoS calculated
via the gas composition) to the SoS using method 1 results in the higher temporal
resolution for the gas composition, respectively the calorific value.
4.3.3
Extended SoS calculation
The third possibility SoS calculation is presented under the name "Extended SoS
measurement". This new method is introduced as an additional determination.
Transducer TD2 receives at first the ultrasonic pulse (light blue) coming from TD1
at the time (t
). This pulse is partially reflected and moves back to TD1 (dark
TD12
blue). There this pulse is reflected, too and reaches TD2 (red) again after the time
(t
). The differences of t
TD12 21 12
culate SoS:
Calculation of extended SoS
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0
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+��
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=
∙
2
��
∙��
����12
����21
( ��
��
����12 21 12
=
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2
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Due to a 10-times smaller variance of the SoS calculation this method offers signif-
icantly more accurate result compared to the standard method (version 1). There
are 2 reasons for this result; first, the transmitter / receiver error is eliminated (es-
pecially T
; the transit time of the pulse in electronic and transducer is different in
W
the individual transducers) and secondly, any flow turbulence in medium has low-
est influence to the transit time (the time interval between t
4 Functional principle – Ultrasonic-flow measurement
Fig. 4.2: Extended SoS calculation
and t
TD12 21 12
TD12
)
−��
����12
−2∙��
)
����12
results in a new possibility to cal-
and t
TD12
TD21
Manual USM GT400 · EN10 · May 2021
41
is as short
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