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3
Commissioning
The load cells are passive sensors. The manual of the weighing module should
therefore be consulted primarily for commissioning. When using in the Ex area, the
instructions for the Ex-i interface or Ex barrier must be observed.
If the reference load of a scales needs to be checked, impermissibly great
deviations in the weight display may occur in load cells which are not electrically
calibrated. This reference load error can be electrically compensated. To do this,
the individual measured values are adjusted to the smallest measured value by
additional wiring. The resistors are connected in series with the load cell measuring
signal. The measuring voltage is reduced by the appropriate resistance until it is
equal to the smallest voltage. Because the resistors are connected in the
measuring circuit, the temperature coefficient must be accordingly low (0.25ppm/K
to 10ppm/K )
Example for reference load adjustment:
Platform scales with 4 load cells, series RN, rated load L
characteristic value C
Figure 3-1 Test diagram
Procedure:
•
Measure output resistances R
LC 1 = 1004.52 Ω
LC 2 = 1003.64 Ω
LC 3 = 1010.70 Ω
LC 4 = 1028.12 Ω
SIWAREX R Load Cells Operating Manual
A5E00159640
=2.0mV/V, test weight =150kg.
n
LC 1
160kg
LC 3
155kg
150kg
of the LC or take them from the data sheet
a
=500kg, rated
n
LC 2
148kg
LC 4
152kg
17
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