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What is a checkweigher used for?

Checkweighers are used for automated weight control of fill quantities in prepackages. The legal basis for this is the Prepackaging Ordinance (FertigPackV, FPackV). The background to the ordinance is the obligation for producers to randomly check the contents of packages for quantities corresponding to the package information. Checkweighers must be calibrated for this purpose.

How do checkweighers work?

Checkweighers used to check fill quantities must comply with so-called "maximum permissible calibration values," depending on the nominal fill quantity. These calibration values each correspond to one digit increment of the scale.

Nominal filling quantity and maximum permissible calibration value:

• less than 10 g/ml - 0.1 g
• 10 to 50 g/ml - 0.2 g
• 50 to 150 g/ml - 0.5 g
• 150 to 500 g/ml - 1.0 g
• 500 to 2500 g/ml - 2.0 g
• from 2500 g/ml - 5.0 g

The operation of checkweighers varies from model to model. Bench scales and smaller checkweighers are usually operated manually, the sample must be placed on the scale and the checkweighing function is performed by reading the display. Most of these scales can be connected to a roll printer.

If the scale has a statistics function, deviations from the preset weight can be automatically evaluated and adjusted if necessary. It is also possible to network several checkweighers via digital interfaces. This allows access to a common article database and eliminates the need to connect each individual checkweigher to a PC.

Checkweigher applications

Checkweighers are mainly used in industrial operations. In the production process, it is important to always have a good overview of article and filling quantities and to be able to quickly correct any malfunctions.

What checkweighers are available?

- Bench scales: Bench scales are particularly suitable for random sample checks of a wide variety of products. They are available in various platform sizes and can be supplemented with printers, data loggers and statistics programs for automated evaluation. Furthermore, several platforms with weighing areas of different sizes can be combined, which enables the simultaneous processing of an extended range of products.

- Counting and checkweigher: Scales that fulfil these two functions are particularly suitable for filling containers with a predefined target number of pieces.

- Checkweigher for +/- correction: Scales of this type enable the input of a specific signal range, the allocation of the correct filling quantity, as well as the automatic correction of deviations from this weighing range.

- Dynamic checkweigher: These are mainly used in industry and consist of several conveyor belts, one of which has a weighing function. The conveyor belts are programmed in such a way that only an exact quantity of an item ever lands on the scale - depending on the item to be weighed, this can also be done by selectively accelerating individual belts. There is thus an interaction between the infeed belt, which takes the article from the upstream machine, one or more acceleration belts, the measuring cell (weighing unit) and a discharge belt, which is capable of rejecting defective products.

Of course, it is possible to combine different types of checkweighers: For example, smaller bench scales can also be combined with conveyor belts or software solutions can be adapted for specific purposes.

All checkweighers are equipped with a display device that has a different range of functions depending on the manufacturer and product. In addition to their main task of displaying weights, the indicators can also be used for counting, dosing and data acquisition.