An increasing number of companies in the field of postal services and logistics maximize their profits with the help of automated weighing systems. Not only is the use of verified scales a legal requirement, it also increases the weighing precision substantially and therefore prevents incorrect billing of postage. Hence, companies using this technology save money on a daily basis.

Exemplary calculation of the potential profit gain of a verified system: 
Due to an imprecise determination of the weights a postal operator bills about 3 per cent of all letters incorrectly. With a daily throughput of about 150,000 standard letters this amounts to a total of 4,500 letters per day which, if the weight had been determined more precisely, should have been billed according to the next higher category. A standard letter of the Deutsche Post costs 0.55€, the next higher category 0.90€. The difference of 0.35€ per incorrectly weighed letter amounts to a potential additional revenue of 4500 x 0.35€ = 1575€ per day which could be realized by the use of a more precise weighing system. The verification ensures that the scales maintain this higher precision over a certain time, the validity period of the verification.

Remark: In the field of parcel logistics additional revenues of more than 2000€ per day are common!

In addition to this profit gain the use of precise and verified scales protects the postal operator from possible fines in the event of an inspection. In the near future these fines can amount to considerable sums. In this context it should be taken into account that even scales which are only kept ready for use are required to be verified, even if they are currently not applied. 

Below you can find a description of a verifiable letter transport weighing system. Furthermore, you can find an overview of the legal requirements for the verification of such scales as well as the prevailing legal practice in Europe and Germany with its resulting consequences.

A typical example for the application of automated scales for the postage determination is their integration into letter sorting systems.

In spring 2008 OCS Checkweighers GmbH, in cooperation with Böwe Bell + Howell, had the first letter transport scale with a speed of 3.4 m/s at PIN Mail Sachsen GmbH in Leipzig verified with a calibration value of just one gram by the Saxon state authority for metrology and verification. This system is based on the established HC series and is implemented as a two track system with two parallel, independent tracks working with a shared alibi memory. The weighcells are based on monoblocks and work according to the principle of Electro Magnetic Force Restoration (EMFR) which allows for highly precise weighing results and high transport speeds.

The letters are conveyed standing on one edge and are dynamically weighed while passing through the system. This facilitates the integration of the scales into the flow of the sorting system and prevents the lift generated by aerodynamic forces at high speeds. Due to the compact design the transport system can be mounted on the weighcell as one complete unit, thus reducing the interference of the transport with the weighing results to a minimum. 

Of course scales of this kind can also effortlessly be integrated into letter sorting systems manufactured by other companies.

OCS Checkweighers GmbH, a subsidiary company of Wipotec GmbH, is the only manufacturer in the whole of Europe to have an EC type examination certificate valid for letter transport scales with speeds up to 4 m/s and a calibration value of 0.5 grams.

The EC type examination certificate was issued based on the long-term cooperation with the Physikalisch-Technische Bundesanstalt in Braunschweig and after successfully completing the approval process.

Additionally, in 2008 OCS and Wipotec obtained the certificate for the approval of their quality management systems according to the measurement devices directive, which entitles the companies to perform conformity inspections according to module D (manufacturer calibration and verification) of the directive. Therefore, all services including the initial calibration can be offered from one hand.

There are still a lot of uncertainties and interpretation problems concerning the question whether a verification is mandatory for scales which are used to determine the postage of letters or parcels. Therefore, the following section summarizes the legal background which does not only apply to standard letters but also to large letters (so-called flats) and parcels.

The verification is a legally required inspection of measuring instruments to test whether they comply with the verification regulations, especially concerning their error margins. It serves the consumer protection and is a requirement to make measuring instruments legal for trade. Especially the last point makes the use of verified scales mandatory for the weighing of letters, since the determined weight is used by a service provider (e.g. a postal operator) to bill the customer accordingly.

European directives are issued to allow for and ensure free trade in the whole of Europe. The measuring instruments directive 2004/22/EC (MID) applies (among others) to automated scales used in trade and makes their verification compulsory.
The MID comprises general requirements for the metrological properties of measuring instruments as well as rules for the verification procedure and defines precision classes and permissible error margins. 

The MID had to be transposed into national law by the EU states by October 2006. In Germany the regulations concerning automated scales were transposed into the verification law (Eichgesetz, EichG) and the corresponding by-law (Eichordnung, EO).

Section 25 of the verification law prohibits the use of unverified measuring instruments for the determination of masses and the corresponding postages as well as keeping unverified measuring instruments ready for use for trade purposes. The same applies to auxiliary systems, such as data processing systems and computer networks, processing the data generated by measuring instruments which are required to be verified. Violations of this regulation can be fined with up to 10,000€ and are always prosecuted and penalized by the metrology and verification authorities. For the future it is expected that the fines will be raised to much higher levels as the draft of the new verification law includes fines of up to 500,000€.

The verification by-law (Eichordnung, EO) regulates the execution of the verification law and therefore represents the German transposition of the requirements of the MID. For example it comprises lists of permissible error margins, precision requirements, validity periods (two years for independent scales for the weight determination of individual mail items) as well as regulations for auxiliary systems. The latter can be exempt from the mandatory verification if they do not interfere with the measuring instrument (absence of retroaction) and if the corresponding measuring instrument or an other verified auxiliary system (e.g. alibi memory) logs the measured values in a way that the records are neither changeable nor deletable.
In addition, the verification by-law defines the exact elements of the above-mentioned fined offences against these regulations. 

Conclusion: The use of verified weighing systems can realize potential profit gains as well as it can prevent legal problems.

Dipl.-Ing. Corinna Hardt studied electrical engineering with a concentration in electrical energy technology and a main focus on electromagnetic compliance at the University of Technology in Kaiserslautern. Since 2008 she works at Wipotec GmbH (Kaiserslautern) in the standards department and is responsible for standards, metrology and certification.