Revision of world-wide applied standard R76 for non-automatic weighing instruments far progressed

The "Organisation International de Métrologie Légale" (OIML) was founded in 1955 to promote the global harmonization in the field of legal metrology. It is an international union of 60 active member states and 50 observing members. Altogether there exist 41 OIML recommendations. If a measuring instrument fulfils the demands of such a recommendation, an OIML certificate is issued. On the basis of this OIML certificate an approval can be issued in a state for this measuring instrument, without measurements to be carried out again.
The OIML recommendation R76 for non-automatic weighing instruments has found increasing application world-wide since its adoption in 1992. Not only in Europe it is turned into national law for 100%, but meanwhile also in e.g. China, Japan and Australia. Since 1992, 615 OIML certificates have been issued on the basis of the recommendation R76. This is 46% of the total number of all OIML certificates issued up to now (1333). Within the last 13 years the weighing instruments have developed metrologically very much and therefore also rose the necessity of a recommendation which stays abreast of the state of the art. Furthermore, an adaptation to other international recommendations concerning the testing methods and test conditions has become necessary (e.g. directives of the "International Electrotechnical Commission" (IEC) dealing with testing of devices on electromagnetic compatibility).
For these reasons the OIML committee TC9/SC1 for non-automatic weighing instruments is dealing with the revision of the OIML recommendation R76 since 2002. This technical committee comprises 26 active member states and 8 observing members. The secretariat which has the function of the technical coordination and the preparing of the revision is composed of France (represented by the "Bureau de la Métrologie, Sous-Direction de la Sécurité industrielle et de la Métrologie") and Germany (represented by PTB).

What was meant at first as a slight adaptation of the recommendation, evolved into a fundamental revision under inclusion of a row of important innovations after a vote on the change requests of the members. Therefore, with the first draft, which appeared at the end of 2003 the recommendation became noticeably larger. Now under the best possible consideration of the suggestions for improvement which have come to this first one and the second draft distributed in 2004 the third and presumably last draft is developed which possibly can be adopted in 2006.

The revised R76 offers more metrological flexibility to the manufacturers of weighing instruments. With the revised recommendation it will be possible to get a certificate after OIML R76 for separate, properly defined modules of the weighing instrument (e.g., for an indicator with A/D conversion or for a terminal). With this solution suitable modules can be combined arbitrarily to a weighing instrument. Another simplification represent the families of weighing instruments which are dealt with in the new R76. A family of weighing instruments contains instruments with the same design features and metrological principles for measurement. The consideration of a family of weighing instruments offers the advantage that for an instrument type the metrologically important parameters are fixed only as ranges. Every weighing instrument of which the metrological data are within this range is automatically covered by the certificate. This means for the manufacturer of a weighing instrument that no new certification procedure is necessary for model variants developed later, provided that the range of the fixed metrological data is kept by the new instrument. This reduces the tests, because only those weighing instruments must be checked of which the metrological data form the border of the fixed range.
Furthermore, an important new section of the R76 is software. While in the present recommendation the software of a weighing instrument remained unconsidered, the new R76 will contain clearly stipulated requirements for the software of weighing instruments and will offer examples of technical implementation, distinguishing between weighing instruments with embedded software an open PC-weighing-systems. Further innovations are, e.g., the treatment of mobile instruments (instruments mounted on or incorporated into a vehicle) as well as requirements for instruments powered from road vehicle power supply.

After the third draft is just finished distributed to the members of the OIML committee for non-automatic weighing instruments in October of this year, a new vote on this draft will be held after three months have passed. Because already with the second draft the most difficult metrological objections were valued and were considered as far as possible and because there exists unity inside the OIML committee not to delay the revision needlessly, no more change requests in respect of the contents are expected for the current draft. Therefore, a soon completion of the works on the revision of the OIML R76 can be expected, possibly before the end of 2006.

Contact person:

Michael Denzel, FB 1.1, AG 1.12, E-Mail: michael.denzel@ptb.de