Omega Speaker Systems High Speed Load Cell Interface Card LCIC-WIM-BEN - Manual (Page 29)

28
3.3.2.4 Filtering
Board’s digital filtering is used to "smooth" the read samplings by
averaging a pre-set number of the internal readings. It's especially essential
on a noisy environment, as this mechanism reduces system's susceptibility
to short interferences. The 'noise' may be either mechanical (e.g., load cell
vibrations), or electrical.
The digital filter averages the raw internal readings of the A/D, whose rate
is 52,734 A/D readings per second. The behavior of the filtering
mechanism is controlled by three parameters:
• Filter1
• Filter2
• Decimator
These three parameters, described below, are adjustable in order to make
them suit best your application.
The filtering mechanism includes two levels:
Level 1
: Each N
1
successive A/D readings are averaged forming the first
level average .
Level 2 : Each N
2
first level averages are re-averaged forming the second
level average . Unlike the N
1
readings of level 1, the N
2
readings of level 2
are not successive: Only each N
3
-th ‘first level average’ participates in the
second level averaging procedure, the other N
3
-1 ones being ignored.
As you might guess, N
1
is Filter1, N
2
is Filter2 and N
3
is Decimator.
The range of Filter1 & Filter2 is selectable from 2 to 256, where 2 is the
lowest
filtering and 256 is the highest filtering.
The range of Decimator is from 1 to 1000.
Note: As described in section 4.1, 4.2 & 4.3.2, user’s application may
select the filtering level it requests – either only Filter1, or Filter2 (=both
Filter1 & Filter2). However, the weight on board’s numeric LED
display is always after Filter2.
3.3.2.5 Filling Definition
The ‘Filling Definition’ box includes the parameters used upon a filling
operation in board’s Fill Mode, as described in section E.4.