How to minimise disrupting influences on weighing results

Cold, heat, air flow: numerous influences can lead to deviations in weighing processes which are undesirable and can only be avoided with suitable weighing technologies and the required background knowledge.

To determine the price of precious metals or industrially used goods, for example, as well as for weighing processes for the exact adherence to specified recipes, absolutely accurate mass determinations with accuracies in the tenths-of-a-gram range are an important prerequisite for correct prices and achieving the required quality. To achieve such high levels of accuracy, numerous factors must be taken into account, and various design measures must be implemented.

As a leading manufacturer of industrial weighing and inspection technologies, Minebea Intec is a reliable partner for the development of fault-free automatic and manual weighing and inspection solutions for a wide variety of applications and industries. Right from the start of the design process for many products, the company takes into account the disrupting influences that can affect weighing processes and integrates suitable technologies to compensate for these influences.

Whether a measurement result actually indicates the exact mass of a product depends on more than just the quality of the scales used. Even if they are correctly installed and adjusted, numerous factors can influence the result despite not being immediately apparent. For example, it is usually assumed that gravity is always the same everywhere on earth. However, this is not the case because the earth is not a perfect sphere and therefore does not have the same density in every location. The distance from the equator and the distance to the centre of the earth also have an impact. Even changing the location of a scale to a higher or lower floor in a building changes the measurement result in the range of 1 ppm, i.e. for a load of 1000 g the weighing result deviates by 1 mg. To reliably avoid such deviations, Minebea Intec offers its customers extensive expertise and numerous engineering services. The company's offerings include mobile, verifiable weighing solutions with an EMFC weighing system (such as the Signum or IS platform models) that also have a built-in calibration weight. Deviations caused by a change of location can thus always be corrected. These systems are extremely flexible and deliver precise measurement results even over several degrees of latitude.

The temperature also has a influence on the measurement results of scales. In particular, heat can cause issues in systems which may manifest themselves, among other ways, as changes in the mechanical dimensions, the generation of forces due to the expansion of the materials used, and changes in the performance of individual weighing components. In extremely cold areas, incorrect weighing results can be caused by ice and snow loads, e.g. on silos, or by temperature errors in the weighing electronics. Industrial scales have to deliver the same results in freezing cold environments as in hot desert regions, the temperatures of which can be more than 100 degrees above those of the Siberian winter. The Engineering Support experts at Minebea Intec have many years of experience with such extreme requirements.

With its high heat resistance, the PR 6212 load cell, for example, ensures reliable processes in sectors such as the chemical and steel industries. The compact product is available in an optional high-temperature version for up to 180°C and absorbs temperature fluctuations through an integrated lifting protection with extended horizontal play. In addition, a high level of vibration resistance ensures precise measurement results even when oscillations occur.

Temperature fluctuations and deviations from the adjusted temperature application range should also be avoided to achieve correct weighing results. If, for example, an industrial scale has an established sensitivity temperature effect of ≤ 2 × 10-6/K ...

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