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Technical Manual
4-4
Data sheet calibration
Data sheet calibration is recommended as first-time calibration for a new installation.
In data sheet calibration, values from the transducer data sheets are entered as
parameter values, the scale need not be loaded and an accuracy of 0.1 % can be
obtained. The accuracy of the G4 Instrument itself is 0.005 % (1-2 years calibration
period). It is essential that no external forces influence the scale installation. If fixed
support points are included in the scale, the load must be evenly distributed on
transducers and fixed supports.
Conv. factor
In transducer data sheets, loads are normally not expressed in the measurement
unit, selected for the scale. This parameter defines a constant by which a weight
value, expressed in the measurement unit, should be multiplied to be expressed
in the data sheet unit.
When using a transducer, calibrated in Newton, in a scale displaying weight values
in kg, the ‘Conv. factor’ shall be the local gravitation constant in m/s
2
.
The default value, 9.80665, is an international mean value for the gravitation
constant (world-wide range 9.78 – 9.83).
If the data sheet unit is the same as the measurement unit, the conversion factor
parameter should be set to 1.0000.
No of Transd
In weighing applications the load on the scale may be supported by several
transducers or fixed supports. This parameter defines the total number of transducers
and fixed supports in the scale, up to maximum 4.
If the scale has more than 4 support points, this parameter should be set to ‘1’
and the parameter value for ‘Rated load’ and ‘Rated output’ must be calculated.
Rated Load
Rated load for a transducer is indicated in the data sheet and should be entered as a
parameter value, expressed in the unit of the data sheet.
NOTE! If the data sheet value is 5 kN, this parameter should be set to 5000 (N).
If several transducers are used in a scale, they must all have the same rated load.
If the scale has more than 4 support points, ‘Number of transd’ should be set to ‘1’
and the value of this parameter should be calculated as:
rated load for one transducer, multiplied by the total number of support points.
Rated Output 1 (2, 3, 4)
Rated output is given in the data sheet for every transducer. Parameters will be
available for the number of support points specified in ‘Number of transd’.
For fixed support points the rated output value is 0.00000 (mV/V).
If the scale has more than 4 support points, ‘Number of transd’ should be set to ‘1’
and the parameter value for ‘Rated output 1’ should be calculated as:
the mean value of rated output for all active transducers.
Set Zero
Set zero is useful only when the scale installation is finished. By the digit keys this
value can be set to zero, for unloaded scale, or to the weight of the known load, for a
scale that is loaded.
The instrument will display actual gross weight when the user attempts to set zero
(pressing enter button when ‘Set Zero’ is selected). Pressing enter button a second
time stops the weight display and the ‘Set Zero’ value can be entered.