Rice Lake Legend 480-2A, Техническое руководство

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Digital Filtering (DIGFIL) 69
9.11.3 Rolling Averaging Filter
The rolling averaging filter uses mathematical averaging with three stages. These configurable stages control the
effect of a single A/D reading on the displayed weight. When an A/D reading is encountered that is outside a
predetermined band, the rolling averaging filter is overridden and the display jumps directly to the new value.
Filter Stages (RFSTG1-3)
The filter stages can each be set to a value of 1 to 64. The value assigned to each stage sets the number of readings
received from the preceding filter stage before averaging. Setting the filter stages to 1 effectively disables the
rolling filter.
A rolling average is passed to successive filtering stages for an overall filtering effect that is effectively a weighted
average of the product of the values assigned to the filter stages (
RFSTG1 x RFSTG2 x RFSTG3
) within a time frame
corresponding to the sum of the values (
RFSTG3
).
Filter Sensitivity (RFSENS) and Threshold (RFTHRH)
The rolling averaging filter can be used by itself to eliminate vibration effects, but heavy filtering also increases
settling time. The
RFSENS
and
RFTHRH
parameters can be used to temporarily override filter averaging and
improve settling time.
•
RFSENS
specifies the number of consecutive A/D readings that must fall outside the filter threshold
(
RFTHRH
) before filtering is suspended.
•
RFTHRH
sets a threshold value, in display divisions. When the specified number of consecutive A/D
readings (
RFSENS
) fall outside of this threshold, filtering is suspended. Set
RFTHRH
to
NONE
to turn off the
filter override.
Rolling Averaging Filter Parameters
1. In setup mode, set the rolling filter stage parameters (
RFSTG1-3
) to 1.
2. Set
RFTHRH
to
NONE
.
3. Return to weigh mode.
4. Remove all weight from the scale, then watch the indicator to determine the magnitude of vibration effects
on the scale.
5. Record the weight below which all but a few readings fall. This value is used to calculate the
RFTHRH
parameter in step 8.
Example – if a heavy-capacity scale (10000x5lb) produces vibration-related readings of up to 50 lb, with
occasional spikes to 75 pound, record 50 pound as the threshold weight value.
6. Place the indicator in setup mode and set the filter stage parameters (
RFSTG1-3
) to eliminate the vibration
effects on the scale (leave
RFTHRH
set to
NONE
).
7. Find the lowest effect value for the
RFSTG1-3
parameters.
If needed, the rolling filter cutout sensitivity (
RFSENS
) and the rolling filter cutout threshold (
RFTHRH
) can be used
to reset the averaging filter so the response to a rate change is faster.
8. Calculate the
RFTHRH
parameter value by converting the weight value recorded in step 5 to display
divisions (
Threshold_Weight_Value / Display_Divisions
).
In the example in step 5, with a threshold value of 50 pound, and a display divisions value of 5 pound,
RFTHRH should be set to 10 display divisions.
9. Set the
RFSENS
parameter high enough to ignore transient peaks. Longer transients (typically caused by
lower vibration frequencies) will cause more consecutive out-of-band readings, so
RFSENS
should be set
higher to counter low frequency transients.