Siemens SIWAREX WL280, Руководство по эксплуатации, Страница: 23 / 58

Application planning
4.4 Overload protection
RN-S SA
Operating Instructions, 09/2016, A5E32605810A-03
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Height compensation of the support points
With this method, the output signals of all of the load cells are attuned to each other under a
load. To ensure that all of the load cells receive approximately the same load, spacer plates
are used to compensate the heights. The spacer plates are positioned between the bracket
and top plate of the installation unit.
The output signals of the individual load cells correspond to the load distribution.
Proceed as follows to measure the output signals:
1.
Disconnect the load cell wires SIG+ and SIG-.
2. Supply the load cells with power from the power supply.
3. Measure the output voltage between SIG+ and SIG- of each individual load cell.
4. Place spacing plates under the load cell bracket with the lowest value until the output
voltages are equal.
4.4 Overload protection
NOTICE
Irreparable faults and damage to the load cells
When using load cells with small rated loads, always provide overload protection in order to
protect the cells from becoming damaged. This applies both to the measuring direction and
the transverse direction.
If load cells are used beyond the maximum working load or the maximum transverse load,
this can cause irreparable faults and even fracturing of the load cell or the installation unit.
Overload protection in the measuring direction
Load cells can be protected against vertical overload by placing a stop screw under the point
where force is introduced. The stop screw limits the measuring path of the load cell.
For load cells with high rated loads, the risk of an unintentional overload is not as great.
Possible additional loads can already be taken into consideration during the dimensioning of
the load cells.
Another method for protecting load cells from an overload is to over-dimension the load cells.
Overload protection in the transverse direction
For the RN-S SA load cells, the weight force is introduced into the load cells via pendulum
bolts. These elements allow lateral movement of the load bearing implement or a change in
its length as a result of expansion due to heat, up to a certain degree. They generate a
restoring force corresponding to the deflection, which re-centers the load bearing implement.
This freedom of movement is desired and necessary for accurate weighing.