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The quantity of materials in tanks and hoppers can only be determined by weight and level measurement. Metering the level is the simpler and cheaper solution, but it is unapplicable in a lot of cases. Weighing is recommended if the material:

• Doesn’t stretch horizontally (like bulging materials),
• Foaming,
• Forbidden to contact with the measuring equipment,
• Its density is changing.

The load cell is outside of the hopper, and this way the aforementioned materials are measurable too. The scale is ideal for controlling and weighing the contents of feeding and mixing hoppers. The construction of the hopper scale depends on many parameters.

The first question is, that if the whole hopper or just a part of it is wanted to placed on load cells. It makes it cheaper if just one side of the hopper is placed on cells, and the other half is fixed with hinges. This solution is only applicable on symmetrical hoppers, and the symmetry has to remain in every level of fullness. In every other cases the whole hopper is needed to be put on load cells.

It is necessary to place load cells in the same plain, horizontally. When placing the hopper the environmental effects must be taken into count (wind, the vibration of the building and the mounting, the flow of the materials), and free horizontal and vertical movement must be provided (bumpers, binding), without affecting the accuracy of the weighing. Special attention must be taken to ensure that appropriate direction forces act on the load cells.
Modes:

• With tensile load cell design, the mandrels have to as long as possible.
• Using compression cell the weighing platform has to be robust, horizontal and hard enough, because it mustn’t distort.

Instrument:

The instrument most suitable for the given weighing task is advised. METRISoft Scalemanufacturer Ltd. offers instruments for every possible need.

• For controlling more than one hopper, but without displaying weight on every terminal: MS-ADT1
• For controlling mixing: MS-MIX
• ...

Factors affecting the accuracy of the weighing:

• Connections on the frame must be soft enough to compensate the forces caused by them
• Fluctuation of temperature (because of the various thermal expansion of the parts)
• Wind
• Contamination, pollution
• Vibration