7.6.2
Shift test
The shift test checks the behavior of the weighing instrument's mechanics and the efects
of full bending of the platform.
On some constructions, this can, e.g., cause an undesirable incline of the load cell under
loading. For that reason, the load cell is equipped with a special measuring element that
sustainably counteracts this efect.
If the construction of the platform has been well designed, the force transmission point of
the load cell is located at the "neutral iber", i.e. the force transmission point does not
shift to the horizontal when the platform bends under loading.
If the force transmission point is markedly above or below the neutral iber, maximum
bending of the platform shifts the force transmission point to the center of the platform
(supporting point above) or to the edge of the platform (supporting point below). The
resulting incline can change the sensitivity and thereby change the weight readout.
The measuring element is specially constructed to counteract this behavior (within limits)
to ensure that even critical constructions maintain calibration error limits. This error can
be eliminated almost completely by intentionally turning the load cells as described in the
table below (derivation from the measured shift error).
The optionally available positioning device ixates the load cell in the desired position.
In most cases, full bending of the platform causes the load cells to incline outwards. Full
bending of the platform and the resulting incline are hardly detectable by the naked eye.
That said, the actions described (see Chapter
7.6.3
) will not be successful unless the load
cells have been previously aligned vertically and the upper load disc is located in the
absolute center on the top of the load cells.
Weighbridge Load Cell PR 6221
7 Preparing for calibration
Minebea Intec
EN-28