Digital Filtering; Digfl X Parameters; Filtering; Dfsens And Dfthrh Parameters - Rice Lake IQ plus 510 User & Installation Manual

7.6

Digital Filtering

Standard digital filtering uses mathematical averaging
to eliminate the variant digital readings that the A/D
converter sends periodically because of external
vibration. Digital filtering does not affect the indicator
measurement rate, but does affect the settling time.
The selections from 1 to 256 reflect the number of
readings averaged per update period. When a reading
is encountered that is outside a predetermined band,
the averaging is overridden, and the display jumps
directly to the new value.
7.6.1

DIGFL x Parameters

The first two digital filtering parameters, DIGFLT1,
and DIGFLT2, 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.
The overall filtering effect can be expressed by
multiplying the values assigned to the two filter
stages:
DIGFLT1 x DIGFLT2
For example, if the filters are configured as
DIGFLT1=16, DIGFLT2=8, the overall filtering effect
is 128 (16 x 8). With this configuration, each A/D
reading has a 1-in-128 effect on the displayed weight
value. Setting the filters to 1 effectively disables
digital filtering (1 x 1 = 1).
®
7.6.2 RATTLETRAP

Filtering

RATTLETRAP digital filtering (RATTRAP parameter
set ON) uses a vibration-dampening algorithm to
provide a combination of the best features of analog
and digital filtering. The RATTLETRAP algorithm
evaluates the frequency of a repeating vibration then
derives a composite displayed weight equal to the
actual weight on the scale less the vibration-induced
flaws. It is particularly effective for eliminating
vibration effects or mechanical interference from
nearby machinery. Using RATTLETRAP filtering can
eliminate much more mechanical vibration than
standard digital filtering, but will usually increase
settling time over standard digital filtering.
7.6.3

DFSENS and DFTHRH Parameters

The digital filter can be used by itself 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:
48 IQ plus 510 Installation Manual
• 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.
7.6.4

Setting the Digital Filter Parameters

Fine-tuning the digital filter parameters greatly
improves indicator performance in heavy-vibration
environments. Use the following procedure to
determine vibration effects on the scale and optimize
the digital filtering configuration.
1. In setup mode, set the digital filter parameters
(DIGFLT1 and DIGFLT2) to 1. Set DFTHRH
to NONE. Return indicator to normal mode.
2. Remove all weight from the scale, then watch
the indicator display to determine the
magnitude of vibration effects on the scale.
Record the weight below which all but a few
readings fall. This value is used to calculate
the DFTHRH parameter value in Step 4.
For example, if a heavy-capacity scale
produces vibration-related readings of up to
50 lb, with occasional spikes to 75 lb, record
50 lb as the threshold weight value.
3. Place the indicator in setup mode and set the
DIGFLTx parameters to eliminate the
vibration effects on the scale. (Leave
DFTHRH set to NONE.) Find the lowest
effective value for the DIGFLTx parameters.
4. Calculate the DFTHRH parameter value by
converting the weight value recorded in Step
2 to display divisions:
threshold_weight_value / DSPDIV
In the example in Step 2, with a threshold
weight value of 50 lb and a display division
value of 5D:
50 / 5D = 10.
be set to 10DD for this example.
5. Finally, set the DFSENS parameter high
enough to ignore transient peaks. Longer
transients (typically caused by lower vibration
frequencies) will cause more consecutive
out-of-band readings, so DFSENS should be
set higher to counter low frequency transients.
Reconfigure as necessary to find the lowest
effective value for the DFSENS parameter.
DFTHRH should