Glossary: weighing technology

Accuracy classes for scales: Combination of different types of scales in classes of equal accuracy. According to the international guidelines of the EC there is the following classification: coarse scale = class (IIII), commercial scale = class (III), precision scale = class (II), fine scale = class (I).

Device for weighing or compensating a tare load without using the weighing range of the scale.

Adjustment is the setting (adjustment) of a measuring chain with the aim of keeping measuring deviations small. An intervention in the measuring chain takes place.

Weight storage for scales requiring W&M approval that evaluate and process the weighing data via a connected EDP system. Electronic archiving by means of a data storage device that conforms to guidelines and cannot be manipulated is required. All data transmitted to the computer (such as date, time, weight) are stored for at least three months.

The alibi printer (log printer) is a printer used to consecutively record weighing transactions for weighing installations with connection to EDP systems.

Type approvals or test reports are issued by a notified body (e.g. PTB in Germany, NMi in the Netherlands). A scale can only be verified if a corresponding valid approval is available.

AWI: Scales where the weighing process is carried out without interaction of the operating personnel.

A distinction is made between:

• Automatic gravimetric filling instruments (AGFI)
• Automaticdiscontinuoustotalizers (bulk weighers)
• Automatic continuous totalizing weighing machines (conceyor belt weighers)
• Automatic checkweighing instruments (checkweighers)
• Automatic railroad scales

Axle weighers or axle load scales are used to determine the axle load of a vehicle. In order to ensure safe transports, a balanced weight distribution on the individual axles of a vehicle is important. Unacceptable overloading of trucks and other vehicles can be avoided with axle load scales and wheel load scales, so that no fines are incurred. Axle load scales belong to the category of truck scales / vehicle scales.

• More regarding vehicle scales

Batch controllers are designed for ... read more

A belt scale is usually installed ... read more

Calibration (calibration) means to determine and document measurement deviations of the measuring device (display) without changing the settings of the measuring chain. The accuracy of the procedure depends on the precision of the reference standards (weights).

I Analytical balance (fine balance), II Precision balance, III Industrial balance (commercial balance).

Working range of the scale. The scale can be loaded up to the indicated weight value as upper limit.

Automatic weighing instrument - read more

Check scales are used to monitor production goods according to weight criteria. A distinction is made between static and dynamic check scales (checkweighers). For static weight checks often plus-minus scales are used.

The German Accreditation Body (DAkkS) is, among others, the successor organization of the German Calibration Service (DKD). A European regulation required the EC member states to establish a single national accreditation body and thus various German predecessor organizations merged to form the DAkkS in 2010. Besides the DKD, these were the German Accreditation Body Chemistry (DACH), the German Accreditation System for Testing (DAP) and the German Association for Accreditation (TGA), to which also the German Accreditation Body Technology (DATech) belonged.

This directive regulates the putting into circulation and the general requirements such as measurement deviation/classification of 'non-automatic weighing instruments'. The technical requirements / tests are governed by the following guideline: OIML R76/EN45501 (NAWI)

The guideline regulates the putting into circulation and the general requirements such as measurement deviation/classification of 'automatic weighing instruments'.

The technical requirements / tests are governed by the following guidelines:

• OIML R61 (AGFI)    = Automatic gravimetric filling instrument
• OIML R51              = Automatic catchweighing instrument
• OIML R51              = Automatic checkweighing instrument
• OIML R107            = Automatic discontinuous totalizer

Discontinuous scales measure and/or control the feeding of masses or batches. They are usually subject to the regulations of the corresponding EC directive or the applicable national regulations.

Scale built into the driveway, which can be driven over by vehicles, for weighing the weight of axles. To determine the total mass of a vehicle, the individual axle loads can be summed up.

Dynamic scales determine the weight of a load during a relative movement between weighing object and load receptor. Examples for dynamic scales are automatic checkweighers or railroad weighbridges.

Dynamic scales determine the weight of a load during a relative movement between weighing object and load receptor. Examples for dynamic scales are automatic checkweighers or railroad weighbridges.

Abbr. for electromagnetic compatibility.

External circumstances that can adversely affect the metrological performance of a scale (such as installation, ambient temperature, weather conditions or electrostatic forces).

Device for gravimetric or volumetric feeding (e.g. screw feeder).

Fieldbus is the generic term for various physically distinct bus systems for automation, production engineering, building automation and automotive technology. There are wired or wireless bus systems with which field devices (sensors and actuators) are connected to the control devices and SCADA systems and which execute the fast data exchange between the individual components.

Filters are used to adapt to the ambient conditions. Shocks and periodic vibrations can be filtered out by several measuring cycles in short succession. The no-motion check prevents a premature reading of not yet final measurement results.

Floor scale: Free-standing platform scale for floor installation.

Weight of a product including packaging or transport container.

Hopper scales play an important role in weight and level determination in trade, production, industry and agriculture. Hopper scales consist of load cells and weighing indicators on which the weight value is displayed. In trade, the verification capability of the weighing electronics is crucial.

The contents of the container can be bulk goods, liquids or gases, for example. Hopper scales are available in various designs. In upright hopper scales, the load cells are attached to the leveling feet. Tension weighing modules are used for suspended installed hoppers.

Information about the ingress protection of housings against dust and water.

• IP65 (according to DIN EN 60529): Suitable for short-term contact with a liquid. Dust-tight.
• IP67 (according to DIN EN 60529): Suitable for short-term use in wet areas. Immersion possible. Dust-tight.
• IP68 (according to DIN EN 60529): Suitable for permanent use in wet areas. Submersion possible. Dust-tight.
• IP69K (according to DIN EN 40050): Completely tight and thus protection of the electrical equipment against penetration of solids and dust. Protection against the ingress of water during high-pressure or steam-jet cleaning

The linearity (also linearity error) of a scale is the maximum deviation of the measured value from the true value over the entire range between the zero point and the maximum capacity of the scale.

According to the EC Directive 90/384/EC, scales must be officially verified if, for example, they are used as follows:

• Business transactions, when the price of a good is determined by weighing.
• Manufacturing of pharmaceuticals in pharmacies and for analyses in medical and pharmaceutical laboratories.
• For official purposes.
• In the manufacturing of prepackaged goods.

Outside the EC, country-specific regulations apply to mandatory verification.

The maximum capacity describes the maximum weight of the load on a scale. This can be read from the type plate or the weighing range sticker.

Measuring bridge: Electrical circuit with several elements for the precise measurement of an electrical quantity, e.g. resistance.

Abbr. for 'Measuring Instruments Directive'.

Pure weight of a product (gross weight minus the weight of the packaging).

Target filling quantity, that a package with a prepackaged good should contain due to legal regulations.

Non-automatic weighing instrument (NAWI): Scales that require operator interaction to operate.

Organisation Internationale de Métrologie Légale. This organization deals with the concerns of legal metrology. The organization issues recommendations that are recognized in many countries and are also implemented in national standards.

Scale for weighing pallets (incl. contents). This can -for instance- be a forklift truck scale.

A programmable logic controller (PLC) is a device that is used to control a machine or system and is programmed on a digital basis.

All planned and systematic activities necessary to provide reasonable confidence that a product or service will meet certain quality requirements ([ISO 9000] 3.2.11). These quality requirements may be defined by the manufacturer of a product himself or may be specified in standards or other normative documents.

Periodic verification of a weighing instrument with subsequent marking by a representative of the competent weights and measures authority.

One or more scales with special functions for the production of recipes, usually with PC or EDP connection for presetting the individual recipe steps and targets.

Reference weights are required for scales with parts counting function. The reference weight is usually obtained by averaging the weight of several parts (reference count). The scale then calculates the total number of pieces and the total weight of the parts.

Measure of consistency for repeat measurements under the same conditions.

Silo scales are used for weight determination - read more

Static scale: There is no relative movement between - read more

Weight of the packaging of a product or container.

(1 Autotare) Feature to reset the weight display of a (partial) weight (e.g. container) standing on the weighing platform to zero by pressing the tare-key. Can be repeated as often as required for electronic scales.

(2 Manual tare) Feature to subtract a tare weight from the weight display by entering a tare weight.

With totalizing, all individual values are added to one value to form a total weight.

The suitability for use in applications requiring W&M approval of a weighing instrument or weighing terminal is documented by the type approval of a Notified Body. For this purpose, the scales or weighing terminals are subjected to a verification test. Conformity to applicable standards in the EC and/or other countries, e.g. OIML, WELMEC, NTEP, Measurement Canada, NMI, etc. is reviewed. This includes both metrological and device-specific requirements. The type approval is documented with the type approval certificate.

A vehicle body scale is a non-automatic scale for weighing the load of commercial vehicles, e.g. garbage trucks. For this purpose load receptors / load cells are installed between the chassis and the body of the vehicle. The influence of the inclination of the vehicle on the weighing is compensated by means of an inclination sensor.

Scale for dispensing a preselected quantity of material by controlling the material flow.

Determination of the mass or weight, respectively, of a sample. Weighing can be static or dynamic.

Static: No relative movement between the sample and the load receptor during weighing. A static weighing is always discontinuous.

Dynamic: Relative movement between the sample and the load carrier during weighing.

Number of weighings per time unit.

Scale with additional equipment that links weighing results to other information and provides output signals (e.g. for controlling or adjusting a process).

By programming upper and lower weight limits, tolerance ranges can be defined e.g. for dosing, filling and emptying.

Check of the filling quantity of prepackaged goods carried out by W&M authorities. The requirements for the filling quantity are specified in the regulations for prepacked goods.

Abbreviation for 'European Cooperation in Legal Metrology'. When the organization was founded, WELMEC stood for 'Western European Legal Metrology Cooperation'. Among other things, the cooperation promotes the exchange of information, the uniform application of European or international regulations, the elimination of trade barriers for measuring instruments and it records special aspects of legal metrology. For these purposes, WELMEC issues recommendations, the so-called 'WELMEC Guidelines', and maintains working relations with national and international bodies.

In addition to the 30 member states of the European Union and the European Free Trade Association (excluding Liechtenstein), WELMEC also includes Turkey and Croatia as associate members. There are also several observing and corresponding organizations, including the 'International Organization of Legal Metrology' OIML.

Wheel load scales are used to determine - read more

Setting the display of the scale to zero.