HF070AEN_v0403_03 Atex_IECEx_CSA_FM
Page 15
5 - SENSOR
FILTER
51
The analog output signal of a sensor does mirror the actual level. This
signal is measured several times a second by the F070-A. The value
measured is a "snap-shot" of the real level as it will be fluctuating. With
the help of this digital filter a 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 there 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
CUT-OFF
52
To ignore e.g. vibration due to an empty tank, a low-level cut-off can be
set as percentage over the full range of 16mA (or 20mA). When the
analog value is less then required with this setting, the signal will be
ignored.
The cut-off value can be programmed is the range 0.0 - 99.9%.
Example:
S
PAN
(setup 13)
R
EQUIRED
CUT
-
OFF
C
UT
-
OFF
(setup 52)
R
EQUIRED OUTPUT
450 L
25 L
25/450 x 100%=5.5%
16mA x 5.5% + 4mA = 4.88mA
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