Saia-Burgess Controls AG
Manual for PCD2|3.W7x0
│ Document 26-
833 E
NG07 │ 2018-10-18
Hardware
1-6
1
Signal processing
Digital filter
The analogue converter is fitted with a low-pass filter with a configurable threshold
frequency between 8 Hz and 800 Hz. This frequency is entered in encoded form
from 20 (800 Hz) to 2000 (8 Hz).
Post-filter
A further low-pass filter can be connected downstream of the converter where
required. This derives the average across 2 to 20 measurements. This filter is
automatically activated when it is established that the object to be weighed is
stable, i.e. the difference between 2 measuring cycles is less than the Gap.
Weighing cycle
Time
Weight
G
A
P
1 2 3 4 5 6
20
Cycle of the converter
Activation of
Post-filter
Value of weighing
available
Time of weighing (Tw)
Throughout the weighing process, interim results can be read off.
Time required for weighing
Of course, this time is dependent on how quickly the items are placed on the
scale. For this description of the behaviour of the measuring equipment, we will
assume that the weighing unit is loaded in sudden bursts. The digital filter requires
4 acquisition cycles to reach the final value. From this point, the post-filter takes as
many acquisition cycles as there are values needed to calculate the average (2 to
20, configurable).
Measurement resolution
The measurement resolution (smallest repeatable weight) is dependent on the
time constants of the digital filter and the post-filter. In general, the resolution of a
measurement is greater, the longer the time available for it. The table below gives
an impression of the relationship between settings, time and resolution.
