Correction Of The Base Line - RMG USM GT400 Operating Manual

The highest value is 100%; under normal conditions it is above 95%. Since 2
measurement paths can fail before the USM-GT-400 loses its calibrated accuracy,
the value may drop down to 66%; if the path failure is caused by a defect trans-
ducer
an immediate repair of the failed transducers should be initiated.
All of these values are given at the display of the USM-GT-400; they are identical
to the values in the RMGView

4.2 Correction of the base line

Correction of the baseline for the velocity
There are several influences (e.g. Reynolds number) resulting in a not exactly pro-
portional relation between the measured and according to the formula 4.5 calcu-
lated mean velocity to the exact mean velocity. Here the following correction helps
to compensate these variations:
Formula, corrected average flow velocity
�� = �� ∙ �� ∙ (1 +
���� �� ��
Legend
=
v
wk
=
K
v
=
F
These values can be used to calculate the process volume flow rate respectively
the corrected process volume flow:
Formula, process volume flow
2
��
��
�� = �� ∙ �� ∙ ∙ 3600 ∙
�� ��
4
Formula, corrected process volume flow
�� = �� ∙ �� ∙ �� ∙
���� �� ����
4 Functional principle – Ultrasonic-flow measurement
USM
.
��
)
100
Corrected average flow velocity
Meter factor
Error from the characteristic curve correction
��
ℎ
2
�� ��
��
∙ 3600 ∙
4 ℎ
(m/s)
Manual USM GT400 · EN10 · May 2021
37