4
2 Functions and features
2.1 Application area
The unit monitors the flow of liquid and gaseous media�
2.2 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 (→ 7.2). 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 speed falls again, the switching status changes if the value "SP
minus hysteresis" is reached�
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.
