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Scale parameters and functions
8.4 Calibration procedure
8.4
Calibration procedure
8.4.1
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)
Calibration weight 1 = 100 kg
Load cell characteristic value
1 mV/V
2 mV/V
4 mV/V
54
equals 326348 digits
equals 1324765 digits
Calibration digit 1 (ca.) when rated load is
500 000
1 000 000
2 000 000
Manual, 07/2014, A5E33715669A-02
SIWAREX WP321
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