Digital Filtering; Digfl X Parameters; Dfsens And Dfthrh Parameters - Rice Lake IQ plus 350 Installation Manual

7.6

Digital Filtering

The IQ plus 350 uses averaged digital filtering to reduce the effect of vibration on weight readings. Adjustable
threshold and sensitivity functions allow quick settling by suspending filter averaging, allowing the weight
reading to jump to the new value. Figure 7-2 shows the digital filter parameters on the CONFIG menu.
DIGFL1
2
4
8
16
32
64
1
Figure 7-2. Digital Filtering Parameters on the Configuration (CONFIG) Menu
DIGFL1=n1
n1
A/D Readings
1st Stage
Filter Average
7.6.1

DIGFL x Parameters

The first three digital filtering parameters, DIGFL1,
DIGFL2, and DIGFL3, are configurable filter stages
that control the effect of a single A/D reading on the
displayed weight. The value assigned to each
parameter sets the number of readings received from
the preceding filter stage before averaging (see
Figure 7-3).
The overall filtering effect can be expressed by
multiplying the values assigned to the three filter
stages:
DIGFL1 x DIGFL2 x DIGFL3
Fo r ex a m p l e , i f t h e fi l t e r s a r e c o n fi g u r e d a s
DIGFL1=4, DIGFL2=8, DIGFL3=8, the overall
fi l t e r i n g e ff e c t i s 2 5 6 ( 4 x 8 x 8 ) . Wi t h t h i s
configuration, each A/D reading has a 1-in-256 effect
on the displayed weight value. Setting the filters to 1
effectively disables digital filtering (1 x 1 x 1 = 1).
DIGFL2 DIGFL3
2
4
8
16
32
64
1
DIGFL2=n2
n2
1st Stage
Filter Averages
2nd Stage
Filter Average
Figure 7-3. Flow Diagram for IQ plus 350 Digital Filters
DFSENS
2 8OUT
4 16OUT
32OUT
8
16
64OUT
32 128OUT
2OUT
64
1 4OUT
DIGFL3=n3
n3
2nd Stage
Filter Averages
3rd Stage
Filter Average
7.6.2

DFSENS and DFTHRH Parameters

The three digital filters can be used by themselves to
eliminate vibration effects, but heavy filtering also
increases settling time. The DFSENS (digital filter
sensitivity) and DFTHRH (digital filter threshold)
parameters can be used to temporarily override filter
averaging and improve settling time:
• DFSENS specifies the number of consecutive
scale readings that must fall outside the filter
threshold (DFTHRH) before digital filtering
is suspended.
• DFTHRH sets a threshold value, in display
divisions. When a specified number of
consecutive scale readings (DFSENS) fall
outside of this threshold, digital filtering is
suspended.
DFTHRH
NONE
2DD
5DD
10DD
20DD
50DD
100DD
200DD
250DD
Displayed
Value
Appendix 39