When the result of a weighing operation determines a selling price, supports a medical decision, establishes a commercial transaction or provides a legally controlled measurement, the reliability of the weighing instrument becomes a matter of legal metrology rather than simply product performance.
Directive 2014/31/EU establishes the European regulatory framework for non-automatic weighing instruments, commonly referred to as NAWIs. A non-automatic weighing instrument is a weighing instrument that requires the intervention of an operator during weighing.
The Directive distinguishes between instruments used for specifically regulated applications and instruments used for other purposes. This distinction is fundamental because instruments used for the regulated applications identified by the Directive must satisfy essential metrological requirements and undergo the applicable conformity assessment before being placed on the market and put into use.
For regulated applications, compliant instruments carry both the CE marking and the supplementary metrology marking. Depending on the conformity assessment route, an appropriately notified conformity assessment body is involved in assessing the instrument or the manufacturer’s quality system.
This GAR Insight explains NAWI scope, regulated applications, accuracy classes, essential requirements, weighing performance, conformity assessment, technical documentation, Notified Body involvement, marking and the route to European market access.
Navigate This Article
Explore NAWI scope, regulated applications, accuracy classes, essential requirements, metrological performance, conformity assessment, technical documentation and CE marking.
Understanding Directive 2014/31/EU
Directive 2014/31/EU harmonises requirements concerning the making available on the market of non-automatic weighing instruments and establishes specific requirements for instruments used for legally controlled weighing applications.
The Directive replaced Directive 2009/23/EC and has applied since 20 April 2016.
What Is a Non-Automatic Weighing Instrument?
A weighing instrument determines the mass of a body by using the action of gravity on that body. It may also determine other mass-related quantities, parameters, magnitudes or characteristics.
Under Directive 2014/31/EU, a weighing instrument is considered non-automatic when it requires the intervention of an operator during weighing.
Non-Automatic Weighing
The weighing operation requires human intervention—for example, placing or removing the load, initiating or controlling the weighing process, or determining acceptance of the weighing result.
Automatic Weighing
The weighing process operates according to a predetermined programme without requiring operator intervention during the weighing operation. Such instruments generally fall outside NAWID and may instead be addressed by the MID where applicable.
Which Weighing Applications Require NAWI Conformity?
Directive 2014/31/EU identifies specific applications for which instruments must satisfy the essential requirements of the Directive. These are situations where inaccurate weighing could affect trade, taxation, health, legal decisions or consumer protection.
Commercial Transactions
Determination of mass for commercial transactions is a regulated application under the Directive.
Tolls, Tariffs & Taxes
Instruments used to calculate tolls, tariffs, taxes, bonuses, penalties, remuneration, indemnities or similar payments based on mass fall within the regulated applications.
Laws & Expert Opinion
Determination of mass for the application of laws or regulations and for expert opinions given in court proceedings is covered.
Medical Weighing
Weighing patients for the purposes of monitoring, diagnosis and medical treatment is a regulated application.
Pharmacy & Laboratory Use
Making up medicines on prescription in a pharmacy and certain analyses carried out in medical and pharmaceutical laboratories are covered applications.
Direct Sales & Prepackages
Determination of price on the basis of mass for direct sales to the public and the making-up of prepackages is regulated.
NAWI Accuracy Classes
Non-automatic weighing instruments subject to the essential requirements are assigned an accuracy class appropriate to their metrological performance and intended application.
Class I
High-precision weighing instruments used where particularly demanding metrological performance is required.
Class II
Precision weighing instruments used for applications requiring a high level of measurement accuracy.
Class III
A widely used category covering many commercial, medical and general legal-for-trade weighing applications.
Class IIII
Instruments intended for applications where the permitted metrological characteristics correspond to ordinary accuracy.
Essential Requirements for Regulated NAWIs
Instruments intended for the regulated applications identified by the Directive must satisfy the essential requirements established in Annex I.
Units of Mass
Measurement results must use permitted legal units and appropriate symbols.
Accuracy
Errors must remain within the maximum permissible errors applicable to the instrument.
Repeatability
Repeated weighing of the same load should provide sufficiently consistent results.
Eccentric Loading
Positioning a load at different locations on the load receptor must not cause unacceptable measurement variation.
Sensitivity
The instrument must respond appropriately to sufficiently small changes in load.
Durability
Metrological characteristics should remain sufficiently stable throughout normal use.
Influence Quantities
Temperature, power supply and other relevant influences must not cause unacceptable measurement errors.
Protection
Components affecting metrological performance require appropriate protection against unauthorised adjustment or manipulation.
Indication
Weighing results must be accurate, unambiguous, non-misleading and easy to read under normal conditions of use.
Accuracy, Repeatability & Eccentric Loading
The core of NAWI conformity is demonstrating that the instrument produces sufficiently reliable weighing results throughout its intended weighing range and operating conditions.
Maximum Permissible Error
The difference between the indicated result and the conventional true value must remain within the limits applicable to the instrument and load range.
Repeatability
Multiple weighings of the same load under substantially identical conditions should produce results within the permitted variation.
Eccentric Loading
The indicated result should remain within the applicable limits when the same load is positioned at different relevant locations on the load receptor.
Sensitivity & Discrimination
The instrument should respond appropriately when the load changes by a relevant amount.
Zeroing, Tare, Displays & Printed Results
Functions that appear routine to the user can have a direct effect on the legally relevant weighing result and therefore form part of the conformity assessment.
Zeroing
Zeroing devices must provide accurate zero setting without producing incorrect measurement results.
Tare
Tare and preset-tare functions must permit correct determination of the relevant net weighing value.
Display
Indicated weighing results must be accurate, unambiguous, non-misleading and readable during normal use.
Printing
Printed weighing results must be correct, suitably identified, clear, legible and sufficiently durable.
Environmental & Electromagnetic Performance
A weighing instrument must maintain its required metrological characteristics under the operating conditions for which it is intended.
Temperature
Temperature changes must not cause weighing errors beyond applicable limits.
Power Supply
Relevant voltage and power-supply variations must not result in unacceptable weighing behaviour.
Electromagnetic Fields
Electronic instruments must maintain acceptable performance when subjected to applicable electromagnetic disturbances.
Electrostatic Effects
Electrostatic disturbances should not produce misleading or uncontrolled weighing results.
Mechanical Conditions
Installation, levelling, vibration and other physical influences should be addressed where relevant.
Connected Equipment
External equipment connected through an appropriate interface must not adversely affect the instrument’s metrological qualities.
EN 45501 & Harmonised Standards
Harmonised standards provide manufacturers with an important technical route for demonstrating conformity with requirements covered by those standards.
EN 45501:2015, Metrological aspects of non-automatic weighing instruments, is the principal harmonised European standard associated with Directive 2014/31/EU.
Metrological Requirements
EN 45501 addresses technical and metrological characteristics relevant to non-automatic weighing instruments.
Performance Testing
The standard provides structured methods for evaluating weighing accuracy and relevant influence factors.
Technical Design
Its provisions support evaluation of instrument construction, indicating devices and other metrologically relevant functions.
Presumption of Conformity
Correct application of a harmonised standard whose reference has been published can provide presumption of conformity for the essential requirements it covers.
NAWI Conformity Assessment
Instruments intended for the regulated applications must undergo an appropriate conformity assessment procedure before the required conformity markings can be applied.
| Conformity Route | Purpose | Typical Third-Party Role |
|---|---|---|
| Module B + Module D | EU-type examination followed by conformity to type based on quality assurance of the production process. | Type assessment plus quality-system assessment and surveillance. |
| Module B + Module F | EU-type examination followed by conformity to type based on product verification. | Type assessment plus verification of production instruments. |
| Module G | Conformity based on unit verification. | Assessment and verification of the individual instrument. |
The manufacturer should establish the conformity route during product-development planning so that design evidence, testing, production controls and Notified Body activities are aligned from the beginning.
↑ Back to Article GuideTechnical Documentation
Technical documentation should enable the conformity of the instrument with the applicable requirements to be assessed and should provide an adequate analysis of the relevant requirements and risks.
CE Marking, Metrology Marking & Instrument Inscriptions
Instruments used for the regulated applications carry the CE marking together with the supplementary metrology marking after conformity has been established.
CE Marking
The CE marking indicates conformity with applicable EU harmonisation legislation requiring that marking.
Supplementary Metrology Marking
The supplementary metrology marking consists of the capital letter “M” and the last two digits of the year in which the marking was affixed, surrounded by a rectangle.
Notified Body Number
The identification number of the Notified Body follows the CE and supplementary metrology markings where required by the applicable conformity assessment procedure.
Metrological Inscriptions
Instruments must carry applicable information such as accuracy class, maximum capacity, minimum capacity and verification scale interval.
Manufacturers, Importers & Distributors
Directive 2014/31/EU places obligations not only on manufacturers but also on other economic operators involved in making instruments available on the European market.
Manufacturer
Ensures that the instrument is designed and manufactured in accordance with applicable requirements and completes the required conformity assessment.
Authorised Representative
May perform specified regulatory tasks on behalf of the manufacturer under a written mandate.
Importer
Must verify specified conformity elements before placing an instrument manufactured outside the Union on the EU market.
Distributor
Must act with due care and verify applicable marking, documentation and traceability requirements before making the instrument available.
Traceability
Economic operators must maintain appropriate information identifying relevant parties in the supply chain.
Corrective Action
Where an instrument is non-compliant or presents a risk, appropriate corrective measures and cooperation with authorities may be required.
From Weighing Instrument Design to EU Market Access
NAWI conformity is most efficient when legal-metrology requirements are incorporated into product development before the instrument reaches final design.
Define Use
Establish the instrument’s intended weighing application.
Confirm NAWI
Determine whether operator intervention makes the instrument non-automatic.
Determine Application
Establish whether the intended use is one of the regulated applications.
Define Class
Establish accuracy class and metrological characteristics.
Map Requirements
Identify the applicable Annex I essential requirements.
Select Standards
Identify appropriate harmonised standards and technical specifications.
Verify Performance
Complete weighing, environmental and other required evaluations.
Build Documentation
Compile technical evidence supporting the instrument’s conformity.
Notified Body
Complete the applicable independent conformity assessment.
Declare
Prepare and sign the EU Declaration of Conformity.
Mark
Apply the required CE, metrology and instrument markings.
Maintain Conformity
Ensure production instruments remain consistent with the assessed design.
From Weighing Capability to Demonstrable Legal-Metrology Conformity
A weighing instrument can display a stable and apparently accurate result without necessarily satisfying the requirements for regulated use in the European Union. NAWI conformity requires the manufacturer to demonstrate that the instrument’s metrological performance, functions, construction and markings satisfy the applicable legal requirements.
The process begins by establishing whether the weighing instrument is non-automatic and determining its intended application. That decision determines whether the essential requirements for regulated use apply.
Where they do, accuracy classification, verification scale intervals, weighing performance, environmental behaviour, software, zero and tare functions, displays, interfaces and protection against manipulation can all become relevant parts of the conformity assessment.
Technical documentation, conformity assessment and production controls should then establish a clear link between the instrument evaluated for conformity and the instrument subsequently manufactured and supplied to users.
The Measurement Question
Does the instrument provide sufficiently accurate, repeatable and reliable weighing results throughout its intended operating range and conditions?
The Regulatory Question
Can the manufacturer demonstrate that the instrument placed on the market corresponds with the metrological design, technical documentation and conformity assessment on which its CE and supplementary metrology markings are based?