Rice Lake Z6 Single-Ended Beam, SS Welded-seal, IP67, OIML C3 - Manual (Page 12)

8 Load Cell and Weigh Module Handbook
5.4 Side Loading
Figure 5-4.
This is a condition where the vertical load F (which you are trying
to measure) is accompanied by a side force R applied at 90° to
F (see Figure 5-4). This force can be constant, but more
typically is a force that varies over time and hence affects the
linearity and possibly the hysteresis of the scale. The ideal load
cell would be totally insensitive to side loads. However, in
practice these extraneous forces do affect the output of the cell
and two seemingly identical cells can react differently to the
same side load. A related condition is the END FORCE, P,
which is similar to a side force, except that it acts on the end
face of the cell. Side forces are typically the result of thermal
expansion/contraction, mounts which are not level, and vessel
dynamics (caused by mixers, etc.).
5.5 Twisting Loads
Figure 5-5.
Typically, a side force does not act exactly at the neutral axis
and hence produces a torque or twisting effect in addition to
the side force. A load cell can be subjected to a torque (T) in a
number of ways. Figure 5-5(a) illustrates a condition where the
line of action of a side force is moved away from the neutral axis
by a distance h resulting in a torque of Rh. Figure 5-5(b)
illustrates a situation where the load is hung from the cell using
a bolt. Any side force applied by this arrangement has a much
larger twisting effect on the cell because of the increased
distance h1 to the neutral axis.
Figure 5-6 illustrates a torque of magnitude Fy exerted as the
result of the load F being applied at a distance y from the
loading hole center line.
Figure 5-6.
Mounts which are out of level as well as thermal expansion/
contraction, structure deflection under load and dynamic side
forces (caused by rotating mixers, etc.) all cause twisting of the
load cell. Since these forces tend to vary in magnitude as a
function of time, temperature and/or load, the effects are not
predictable, and will degrade system accuracy.
F
R
P
R
R
h
(a) (b)
h
1
T
T
F
y