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3 Functions and features
3.1 Application area
The unit monitors the flow of liquid and gaseous media�
3.2 Operating principle flow monitoring
•
The unit detects the flow speed to the calorimetric measuring principle and
switches the output:
-output closed if medium is flowing / output open if no medium is flowing�
This applies to the unit on delivery: output = normally open� In case of need you
can change the output to normally closed (→ 8.2). It then applies: output open
if medium is flowing�
•
If the flow speed increases, the switching status changes when the switch point
is reached�
•
If the flow velocity falls again, the switching status changes when the value „SP
minus hysteresis“ has been reached and the switch-off delay has elapsed�
The switch-off delay starts when the value „SP minus hysteresis“ has been
reached and is 5 s (for SI0519) / 15 s (for SI0520)�
The hysteresis changes with the flow speed and it is essentially influenced by
the set monitoring range�
It is 2���5 cm/s for the setting 5���100 cm/s (= factory setting), it increases with
higher flow speeds�
•
The typical response time of the unit is 1���10 s� It can be influenced by the
setting of the switch point:
-Low switch point = quick reaction with rising flow�
-High switch point = quick reaction with falling flow�
3.3 Operating principle temperature monitoring
When medium temperature > 70 °C output switches back�
