volume should be at 90 % level, these are 9538 litres with a standard
vessel (according to bearing chart). The min. level should be adjusted
to 5 %, this corresponds to 181 litres. The volume should be displayed
in litres.
Carry out the adjustment in the signal conditioning instrument as
described in chapter "Setup steps". No additional adjustment must
hence be carried out on the sensors. For the max. adjustment, fill the
vessel up to the requested max. level and accept the actually
measured value. If this is not possible, the respective current value can
be entered alternatively. For the min. adjustment, empty the vessel up
to the min. level or enter the respective current value.
To display the percentage level correctly, select under "Measurement
loop - Linearization curve" the entry "Cylindrical tank".
The display the volume in litres, you have to enter under "M easure-
ment loop - Scaling" as unit "Volume" in litres. Finally, the allocation is
carried out, in this example 100 %
≙
10000 litres and 0 %
≙
0 litres.
Percent is selected as reference value for the relays. The mode of
relay 1 is set to overfill protection, relay 2 gets mode dry run protection.
To ensure that the pu mp switches off in case of failure, the reaction in
case of failure should be adjusted to switching status OFF. The
switching points are adjusted as follows:
l Relay 1: Switch off point 90 %, switch on point 85 %
l Relay 2: Switch off point 5 %, switch on point 10 %
Information:
The switch on and off point of the relays must not be adjusted to the
same switching point because this would cause a permanent switchin
on and off when this threshold is reached. To avoid this effect also with
fluctuating product surface, a difference (hysteresis) of 5 % is useful
between the switching points.
8.2 Pump control 1/2 (running time controlled)
Pump control 1/2 is used to control several pumps with the same
function dependent on the previous running time. The pump with the
shortest running time is always switched on and the pump with the
longest running time switched off. In case of higher requirements, all
pumps can also run at the same time dependent on the entered
switching points. Through this measure, a balanced utilization of the
pumps is achieved and the reliability increased.
All relays with activated pump control are not assigned to a certain
switching point but are switched on or off depending on the operating
time. The signal conditioning instrument selects the relay with the
shortest operating time when the switch-on point is reached, and the
relay with the longest operating time when the switch-off point is
reached.
Operation
Linearisation
Scaling
Relay
Functional principle
VEGAMET 624 • 4 … 20 mA/HART signal conditioning instrument 37
8 Application examples
28969-EN-091116
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