Vega VEGAMET 624 - Flow Measurement

l Select under "Reaction in case of failure" the option "Switching
condition off"
l Enter the following values into the parameter fields:
- Measured value more than 25 %/min.
- Max. reaction time 1 min.
The function of the tendency recognition is shown in detail in the
following diagram. The previously described example is used as a
basis.
t
t
m
t
m
t
m
t
m
120 180 240
ON
OFF
60
[sec]
1 2 3 4
5
...
... ... ...
100
75
50
25
0
%
...
Fig. 12: Example for tendency recognition
1 Old average value = 25 %, new average value = 25 %
Difference < 25 % -> Relay ON
2 Old average value = 25 %, new average value = 37.5 %
Difference < 25 % -> Relay ON
3 Old average value = 37.5 %, new average value = 62.5 %
Difference = 25 % -> Relay OFF
4 Old average value = 62.5 %, new average value = 75 %
Difference < 25 % -> Relay ON
5 tm -> max. reaction time
8.4 Flow measurement
For flow measurement in open flumes, a contraction or standardised
flume must be used. Depending on the flow volume, this contraction
generates a certain backwater. The flow can be determined from the
height of this backwater. The flow volume is outputted by an
appropriate number of pulses on the relay or current output.
Depending on the type and version, each flume generates a different
backwater. The data of the following flumes are available in the
instrument:
l Palmer-Bowlus-Flume
l Venturi flume, trapezoidal weir, rectangular weir
l V-Notch
Setup
The configuration of the flow measurement loop requires PACTware
with the suitable DTMs. The example refers to a flow measurement
with a radar sensor. The following setup steps must be carried out:
Functional principle
Flume
40 VEGAMET 624 • 4 … 20 mA/HART signal conditioning instrument
8 Application examples
28969-EN-091116