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Application of the modular concept with weighing instruments

26.03.2009

In the second issue of the OIML-Bulletin of 2009 (OIML = Organisation Internationale de Métrologie Légale) an article about the application of the modular concept has been published by employees of Department 1. The motivation to do so were difficulties on the part of the BIML as well as on the part of some OIML members in metrological interpretation of the modular concept presented in the latest issue of OIML recommendation R76-1 (Metrological aspects of nonautomatic weighing instruments) dated 2006.

Therefore, the article initially shows that the modular concept with weighing instruments originates from the 1988 issue of R76-1, although it has been described in detail not until the issue of 2006. The article shows the original intention of the modular concept. It aimed at developing test procedures for weighing instruments that could not be tested in laboratory due to their large dimensions. A further goal was to offer the option of a separate test of modules to manufacturers of e.g. load cells (Fig. 1) and indicators (Fig. 2), aiming at merchandising these modules as certified components of a weighing instrument subject to legal control. Thus, the article also lists modules that can be separately tested and certified. Simultaneously, a general clause for mechanical design of load receptors within R76-1 is presented, also proposing how a mechanically correct construction can be made sure. Furthermore, the article describes and shows that the modular concept can be also applied to automatic weighing instruments without restrictions, provided the load to be weighed is not in relative movement to the load receptor. Yet, it is explicitly indicated that automatic weighing instruments as a whole shall undergo an additional test on site.

The authors assume that the publication will lead to a better acceptance of the modular concept and thus a worldwide use without reservations.

Load cells with different measuring ranges

Figure 1: Load cells with different measuring ranges

Indicator

Figure 2: Indicator

Contact person:

Karsten Schulz, FB 1.1, AG 1.13, E-Mail: karsten.schulz@ptb.de