Rice Lake Survivor 390HE Hostile Environment Digital Indicator - Manual (Page 39)

Appendix 35
8.6 Digital Filtering
The 390HE 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 8-3 shows the digital filter parameters on the CONFIG menu.
Figure 8-3. Digital Filtering Parameters on the Configuration (CONFIG) Menu
Figure 8-4. Flow Diagram for 390HE Digital Filters
8.6.1 DIGFLx 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 8-4).
The overall filtering effect can be expressed by
multiplying the values assigned to the three filter
stages:
DIGFL1 x DIGFL2 x DIGFL3
For example, if the filters are configured as
DIGFL1=4, DIGFL2=8, DIGFL3=8, the overall
filtering effect is 256 (4 x 8 x 8). With this
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).
8.6.2 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. Set DFTHRH to NONE to turn off
the filter override.
1
2
4
8
DIGFL1
32
16
64
1
2
4
8
DIGFL2
32
16
64
1
2
4
8
DIGFL3
32
16
64
8OUT
32OUT
16OUT
64OUT
DFSENS DFTHRH
2OUT
128OUT
4OUT
2DD
NONE
5DD
20DD
10DD
50DD
200DD
100DD
250DD
DIGFL1= n1 DIGFL2= n2 DIGFL3= n3
3rd Stage
Filter Average
2nd Stage
Filter Average
1st Stage
Filter Average
Displayed
Value
n3
2nd Stage
Filter Averages
n2
1st Stage
Filter Averages
n1
A/D Readings