Thermo Scientific HB-S2000, Руководство пользователя

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Sarasota 2000 Ultrasonic Multipath
Flowmeter
Section 1 INTRODUCTION Page 1-3 Thermo Fisher Scientific
INTRODUCTION
The mean water velocity at the height of each path is determined from these timing
measurements, based on pre-determined geometrical measurements (length of the path and
the angle to the flow direction).
It may be shown that the water velocity at the height of the path AB is:
v = L x (T
AB
– T
BA
) / (T
AB
x T
BA
x 2 cos
θ
)
Where
T
AB
= Transit time from transducer A to B
T
BA
= Transit time from transducer B to A
L = Path length (distance between transducer A and transducer B)
θ
=
the angle between the “path” and the direction of flow.
1.2.5 Flow determination
The flow is determined by combining the water velocity measurements at the height of each
path with the cross section area defined by the water level and the shape of the channel. The
channel shape need not be the same as the projected width between the transducers. For
example if the transducers are mounted on piles inset from the channel sides. For the
purposes of flow determination the cross section area is divided into horizontal slices
determined by the channel bed, the heights of the paths themselves and the water surface
level.
The channel flow is the sum of the flows in each slice determined by the path velocity or
velocities and the area of the slice. The bottom slice is defined by the bed (which is assumed
not to move) and the top slice by the water level (which is measured). The slice widths may
be determined by the projected width between the transducers or by a separate table defining
the cross section shape.
There are 2 methods, mid section and mean section.
Transducer A
V
Transducer B
Ultrasonic Path
Direction of the Flow
θ