HF110AEN_v0501_04
Page 16
5 - FLOWMETER
SIGNAL
51
The F110-A can process the 4-20mA signal in two ways:
Interpolation: the signal is processed linear
R = S x I
Square root: for differential pressure
R = S
√
I
where:
R = Rate: the calculated flowrate
S = Span: the maximum flowrate at 20mA. The span is programmed
with setting 24 for flowrate and with setting 13 for total.
I = Input: the scaled analog value; in these formulas value 0 (zero)
for (0)4mA and value 1 (one) for 20mA.
FILTER
52
The analog output signal of a flowmeter does mirror the actual flow. This
signal is measured several times a second by the F110-A. The value
measured is a "snap-shot" of the real flow. With the help of this digital
filter a more stable and accurate reading can be obtained while the filter
level can be set to a desired value.
The filter principal is based on three input values: the filter level (01-99),
the last measured analog value and the last average value. The higher
the filter level, the longer the response time on a value change will be.
Below, several filter levels with their response times are indicated:
F
ILTER VALUE
R
ESPONSE TIME ON STEP CHANGE OF ANALOG VALUE
.
T
IME IN SECONDS
50%
INFLUENCE
75%
INFLUENCE
90%
INFLUENCE
99%
INFLUENCE
01
filter disabled
filter disabled
filter disabled
filter disabled
02
0.3 seconds
0.5 seconds
1.0 seconds
1.8 seconds
03
0.5 seconds
1.0 seconds
1.5 seconds
3 seconds
05
1.0 seconds
1.8 seconds
2.8 seconds
5.3 seconds
10
1.8 seconds
3.5 seconds
5.6 seconds
11 seconds
20
3.5 seconds
7.0 seconds
11 seconds
23 seconds
30
5.3 seconds
10 seconds
17 seconds
34 seconds
50
8.8 seconds
17 seconds
29 seconds
57 seconds
75
13 seconds
26 seconds
43 seconds
86 seconds
99
17 seconds
34 seconds
57 seconds
114 seconds
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