Burkert Type 8611 - Manual (Page 72)

72
FunctionsoftheConfigurationLevel
12.12. FILT - filtering of the process actual value input
Factory setting: FILT = 08
Value range: 2 - 20
The process actual value input is prepared via a digital FIR filter for the control or for the analog process value output.
The behavior of such filter corresponds to an analog filtering using an RC element. The time behavior of the filtering
differs depending on the measuring signal (frequency signal or analog signal).
12.12.1. filtering analog inputs (4 - 20 ma, 0 - 10 V, pt 100)
The analog measurement values are scanned at a sampling frequency of 300 Hz, the resulting sampling rate
amounts to 3.33 ms
The time behavior of the measurement value depending on the filtering depth is shown in the figure below.
Jump signal
Filtering depth 2
Filtering depth 4
Filtering depth 6
Filtering depth 8
Filtering depth 12
Filtering depth 16
80 130 180 230 280 330 380
12
10
8
6
4
2
0
time in [ms]
Measuring
signal
Figure 53: Filtering of the analog measurement values depending on different filtering depths
The T
90
time as response to a jump signal can be estimated as follows:
t
90
= 2.2 x sampling rate (3.33 ms) x filtering depth = 7.3 ms x filtering depth
12.12.2. filtering frequency inputs
For frequency inputs, the sampling frequency for filtering the flow-rate value varies. It depends on the selected flow-
rate sensor. The typical output frequencies for the Bürkert flow-rate sensor range between 10Hz and 200 – 300
Hz. The measured period T
p
serves as the measure for estimating the T
90
time. Based on this period, the T
90
time
can be estimated as follows:
t
90
= 2.2 · period · filtering depth
The following table contains a list of the frequency range (f
min
- f
max
) and the period (T
p
) for the Bürkert flow-rate
sensors that are stored in the eCONTROL Type 8611. Sampling frequencies under f
min
are automatically detected
by the eCONTROL Type 8611 as zero flow-rate.
sensor type 8011, 8012,
8030, s030 8031 s070 8071 8081 free
Frequency range [Hz]
f
min
- f
max
3 - 255 15 - 283 1 - 72 0,5 - 55 0,5 - 666 0,5 - 2000
Period [ms]
T
p
333 - 4 66 - 3,5 1000 - 14 2000 - 18 2000 - 1,5 2000 - 0,5
Table 26: FILT, frequency range and period of Bürkert flow-rate sensors
english
Type 8611