17
4 Mounting
VEGAPULS 11 • Two-wire 4 … 20 mA
58350-EN-221027
Fig. 15: Agitators
Through the action of filling, stirring and other processes in the vessel,
compact foams which considerably damp the emitted signals may
form on the medium surface.
Note:
If foams lead to measurement errors, you should use the biggest pos-
sible radar antennas or as an alternative, sensors with guided radar.
4.3 Measurement setup - Flow
In general, the following must be observed while mounting the device:
•
Mounting the sensor on the upstream or inlet side
•
Installation in the centre of the flume and vertical to the liquid
surface
•
Distance to the overfall orifice or Venturi flume
•
Distance to the max. height of the orifice or flume for optimum
accuracy: > 250 mm (9.843 in)
1)
•
Requirements from approvals for flow measurement, e.g.
MCERTS
Predefined curves:
A flow measurement with these standard curves is very easy to set
up, as no dimensional information of the flume is required.
•
Palmer-Bowlus flume (Q = k x h
1.86
)
•
Venturi, trapezoidal weir, rectangular flume (Q = k x h
1.5
)
•
V-Notch, triangular overfall (Q = k x h
2.5
)
Channel with dimensions according to ISO standard:
When selecting these curves, the dimensions of the flume must be
known and entered via the assistant. As a result, the accuracy of the
flow measurement is higher than with the specified curves.
Foam generation
Mounting
Flume
1)
The value given takes into account the block distance. At smaller distances,
the measuring accuracy is reduced, see " Technical data".
