VEGA VEGAMET 391 With SIL qualification - Manual (Page 38)

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9 Application examples
VEGAMET 391 • With SIL qualification
38704-EN-130228
fies the relationship between percentage level and vessel volume. If
the level should be displayed on the sensor in litres, a scaling must
also be carried out. For this purpose, the linearized percentage value
is converted into a volume, e.g. in the unit "litre." If the signal condi-
tioning instrument should also display the level in litres, the scaling
must also be carried out in the signal conditioning instrument.
Note:
The settings for the indication of the signal conditioning instrument
(adjustment, linearization and scaling) do not influence the safety
function of the SIL relay.
For the application "Dry run protection", the relay mode "Dry run
protection" is set for SIL relay 3. The relay is thus switched off when
the level falls below the min. level (switching point Lo) (safe current-
less status), and switched on again when it exceedes the max. level
(switching point Hi).
0% = 4 mA
5% = 4,8 mA
40% = 10,4 mA
100% = 20 mA
1
2
3
Fig. 9: Dry run protection according to SIL2
1 SIL relay 3 of VEGAMET 391 mit SIL-Qualifikation
2 Upper switching point Hi (ON) of SIL relay 3
3 Lower switching point Lo (OFF) of SIL relay 3
A cylindrical tank has a capacity of 10000 litres. The measurement is
carried out with a level sensor operating according to the principle of
the guided microwave. Emptying is carried out by a pump controlled
via a PLC. Relay 3 of VEGAMET is connected to prevent dry running
of the emptying pump. The min. filling level should be set to 5 %,
which corresponds to 181 litres in a standard vessel (according to
sounding chart). The filling quantity should be displayed in litres.
Carry out the adjustment as described in the respective operating
instructions of the sensor. After that, further adjustment must not be
carried out on the signal conditioning instrument.
To have the percentage volume displayed correctly, a lineariza-
tion must be carried out. As described in the respective operating
instructions of the sensor, select the linearization curve "Cylindrical
Example
Adjustment
Linearisation