5 | Parameterization
FISCHER Mess- und Regeltechnik GmbH
58 / 88
BA_EN_EA16
Explanations about dynamic filter monitoring
Δp
V
Δp
Δp SUP
W
1
2
3
4
5
6
7
Fig. 81:
Filter monitoring principle sketch
1
Zones with variable supply air volume flow
2
Supply air pressure control with ventilator speed control
3
Differential pressure sensor of the filter monitoring (
channel dP
)
4
Flow rate sensor (
Channel 1 V
)
5
Target value guide encoder
6
Difference pressure controller of the filter monitoring
7
Air filter - fault message
The air filter in this example has the task of retaining dust-like soiling from the
outside air. As the soiling increases, the differential pressure measured above
the filter increases. As soon as the differential pressure exceeds the set limit,
the filter sensor reports that the filter is soiled. This is shown as a malfunction.
The flow rate control keeps the air flow rate constant despite an increase in soil-
ing by raising the ventilator speed. The pressure drop above the air filter does
not, however, just depend on the level of soiling, but also the size of the flow
rate.
The pressure drop will change in the flow rate squared. Therefore, a reduction
of the flow rate from 100 % to 50 % means a reduction of the pressure loss
above the filter element from 100 % to 25 %.
20
40
60
80
100
20
40
60
80
100
25
50
Δp [%]
V [%]
Fig. 82:
Dependency on the volume flow
To be able to determine the level of soiling in a differential pressure measure-
ment, it is therefore necessary to carry out the measurement at the maximum
flow rate. This is measured at regular intervals.
