8.4.17 Mean value filter depth
The mean value filter is used to steady the weight against random interference. The weight is
the mean value of n (n = max. 250) weights which are recorded by the weighing module every
10 ms, e.g. when n = 10, the mean of 10 weights is calculated. Every 10 ms, the oldest value
is discarded and the newest value included in the calculation.
8.5 Calibration procedure
8.5.1 Calibration with calibration weights
The incoming analog measured value from the load cells is converted into a digital value in an
analog-to-digital converter. A weight is calculated using this digital value. This weight is then
used by all weighing module functions for messages and for determining the status.
The characteristic curve of the measuring system must be defined before the weight can be
calculated from the digital value. In the simplest case, the characteristic curve is defined with
points 0 and 1. The first working point (point 0) is defined by the empty scale (no load) at their
own weight. The load cells return a voltage measurement to the weighing module as a result of
the weight of the scales themselves. Following analog-to-digital conversion of the measured
voltage, the zero point is assigned to the digital value (calibration digits for the zero point).
If the scales are loaded with a defined standard weight (e.g. 50% of the measuring range), the
new digital value returned by the analog-to-digital converter is assigned the standard weight.
The characteristic curve can also be determined with a third point, which must be higher than
point 1.
Make sure that the difference between two calibration weights is at least 40 000 digits, as the
calibration command may otherwise be rejected.
The calibration procedure involves the following steps:
● Activation of service mode using the "Service mode on" command.
● Define the calibration weight and other parameters of the DR 3 data record.
● Transfer the DR 3 data record to the scales.
● Trigger "Adjustment weight 0 valid" for empty scales.
● Load the scale with the defined standard weight.
● Trigger "Adjustment weight 1 valid".
● Transfer data record DR 3 from the scale to SIWATOOL and save the data on a data
medium.
You must follow the correct calibration sequence with increasing calibration weights.
Example
Zero point = 0.0 kg (always) equals 326348 digits
Calibration weight 1 = 100 kg equals 1324765 digits
Scale parameters and functions
8.5 Calibration procedure
SIWAREX WP321
Operating Instructions, 08/2019, A5E33715669A-AD 67
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