4BWEIGHING FUNCTIONS
5.2.3
DR3/4 - Adjustment digits for the adjustment zero, adjustment digits and
adjustment weight
The analog signal arriving from the load cells is converted into a digital value in an
analog-digital converter. Then a weight value is calculated from this digital value.
All functions of SIWAREX U then use this weight value for the status determination
and messages.
To calculate the weight value from the digital value, the characteristic curve of the
measurement system must be determined. The characteristic curve is determined
using the operating points 0 and 1. The first operating point (point 0) is always
determined by the empty scale alone with its own construction weight. Through the
weight of the scale's own construction, the load cells deliver a measured voltage to
SIWAREX U. After the analog-digital conversion of the measured voltage, the zero
point is assigned to the digital value (adjustment digits for the adjustment zero) with
the command "Adjustment zero valid (1)".
If the scale is loaded with a known calibration weight (e.g. 100% of the measurement
range), the second operating point can be determined. The new digital value from the
analog-digital converter is now assigned the calibration weight.
Ensure that the difference between two adjustment weights is at least 5% of the
measurement range.
The adjustment consists of the following steps:
Define the adjustment weight and other parameters of the data record DR3 or
DR4.
Send DR3 or DR4 to the scale
When the scale is empty, actuate the command "Adjustment zero valid (1)"
Load the scale with the defined calibration weight
Actuate the command "Adjustment weight valid (2)"
Receive DR3 or DR4 from the scale
Save the data as scale file on data carrier
The adjustment sequence for the increasing adjustment weights must be retained.
Example:
Adjustment zero = 0.0 kg (always)
results in 7800 digits
Adjustment weight = 100 kg
results in 52324 digits
The characteristic curve is thereby determined and the scale can now calculate the
weight values for the entire measurement range.
Note:
Since the theoretical maximum terminal value for adjustment digits is 63107 and
the value for completely empty load cells (without their own construction weight) is
2427, the plausibility of the characteristic curve can be roughly tested in order, for
example, to detect force shunts.
5-30
SIWAREX U
Summary of Contents for Siwarex U
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