5 | Operation FISCHER Mess- und Regeltechnik GmbH
76 BA_EN_DE90
Square-root approximation of the characteristic curve
If the filter characteristic curve is strongly curved, a more exact approximation
may be necessary. In this case, the Approximation parameter can be set
to the ‘Square-root' value.
The software then calculates a square root characteristic from the other para-
meters.
50
Δp
Q
1
100
150
200
250
300
2 3 4 5 6 7 8 9 10
[1000 m
3
/h]
[Pa]
filter characteristic curve
soiled filter
filter characteristic curve
clean filter
Q
min
Q
max
Δp
max (soiled)
Δp
max (clean)
square root approximation
Fig.108: Square-root approximation of the filter characteristic curve
The ∆p correction value parameter can be used to set an offset for the
linear characteristic curve so that the deviation from the real filter characteristic
curve is minimized over the entire operating range.
50
Δp
Q
1
100
150
200
250
300
2 3 4 5 6 7 8 9 10
[1000 m
3
/h]
[Pa]
Q
min
Q
max
Δp
max (soiled)
Offset
0%
100%
corrected filter characteristic
curve soiled filter
soiled filter
clean filter
filter characteristic curve
soiled filter
display range
[%]
Soiling
Volume flow
Operating point
Fig.109: Correction value square-root filter characteristic curve
With the parameters Displ.range C3 start and Displ.range C3
end the display characteristic curve can be spread appropriately. Since the
limit curve for the contaminated filter is now fixed, the degree of contamination
of the filter can be determined dynamically for any operating point.
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