Benchtop Scales

For some applications, the verified benchtop scales must be used. This provision is intended to ensure that in commercial transactions, official measures and medical applications, nobody suffers financial or health damage as a result of the inaccurate determination of weights.

This applies to the following areas of application, among others:

• the weighing of goods, if the weight affects the price,
• the weighings the result of which is the basis for calculating a fee, for example postage or customs,
• the weight determination for the expert opinions that can be used in court,
• the weight determination for determining the amount of fines or penalties,
• the weighing for medical or pharmaceutical purposes.

For the applications that are not subject to verification, a very high accuracy of the weighing results can also be guaranteed in the case of the benchtop scales by means of the regular calibration with the suitable, tested calibration weights. Depending on the requirements, calibrations can be carried out in-house or by the specialized calibration laboratories. In the Federal Republic of Germany, however, official verifications may only be carried out by the responsible verification office.

In addition to the criteria that are important when purchasing any scales, such as weighing range, resolution, design, platform size, display design and operating functions, other features must also be taken into account with the verified benchtop scales. This includes the accuracy class, the spatial scope of the verification and the labelling of the scales as well as the associated documents.

There are four accuracy classes for the verified scales defined in EU Directive 2014/31. Classes I to IIII differ in the verification value, in the number of possible display values as a multiple of the verification value and in the minimum load above which the scales may be used as the verified scales. For the verified scales, the verification value "e" indicates the display steps in which a weighing result is displayed instead of the resolution "d".

Class I is the accuracy class with the highest requirements, it is used for the exact determination of the smallest amounts. The accuracy class IIII is only approved for weighing large quantities with a low price per kilogram or ton. Since these goods are not usually weighed on the benchtop scales, only accuracy classes I, II and III are relevant for the verified benchtop scales. Some companies, shops, pharmacies and laboratories require scales for each of the three accuracy classes.

In general, the lower the weights that are to be determined are, the smaller the calibration value and thus the accuracy class must be.

The verified benchtop scales of accuracy class I has a calibration value of 0.001 grams. Due to the high weighing accuracy and the internal adjustment, it is more expensive and sensitive than the scales of accuracy class II or III. Due to its sensitivity, it may only be used within a narrowly limited temperature range and must be protected as well as possible against temperature fluctuations, vibrations and electromagnetic radiation. The measured values of these verified fine scales are often displayed with an additional decimal place. Here the resolution d and calibration value e are not identical. The resolution, which is usually 10 times finer, is displayed significantly differently so that it is immediately recognized as an auxiliary display.

In contrast to the types with accuracy class 1, the verified benchtop scales of accuracy class II does not have to be equipped with an internal adjustment. In addition, the weighing range and the temperature range in which they can be used are larger. The verification value can have values from 0.001 grams to more than 0.1 grams. These scales are used, for example, as analysis scales and recipe scales in industry, in pharmacies and in medical and pharmaceutical laboratories.

The calibrated benchtop scales with accuracy class III are sufficient for many applications. This applies to baby scales in hospitals as well as to postal or parcel scales, scales in shops or scales for direct sale at the market, directly on the farm or in the farmer's field. Accuracy class III scales can also usually be used to check the filling weight of the finished packaging, the contents of which are billed by weight. As a rule, these scales can display significantly fewer values than scales of classes I and II and are less complex in construction.

With many scales, the weight determination depends on the gravitational value at the installation site. The gravitation must therefore be taken into account during the adjustment. The verified scales can no longer be adjusted after verification or conformity assessment without damaging the verification seal. The verification therefore becomes invalid when the scales are readjusted. A gravitation-dependent verified benchtop scales must therefore be set to the gravitation value of the installation site before verification. Therefore, when ordering the verified scales, the postal code and the location in which it is to be used is requested.

The scales of the accuracy class M I make an exception, as they are equipped with an automatic internal adjustment function and are therefore independent of gravitation. For the other scales, the label on the scales housing and the documents state the geographic area for which the calibration applies. For the scales of accuracy class III, the gravitational value of 9.81 g/m² is sufficient for the whole of Germany. However, the benchtop scales verified for Germany with this setting may not be used as the verified scales in Poland, Austria, Belgium or the Netherlands.