NAWI and MID Directives Explained for Marine Scale Buyers

Two EU directives govern the metrological conformity of scales: Directive 2014/31/EU for non-automatic weighing instruments (NAWI) and Directive 2014/32/EU, the Measuring Instruments Directive (MID), whose Annex VIII covers automatic weighing instruments. Both have applied since 20 April 2016. This guide explains what each covers, what the CE and M markings mean, the role of notified bodies and when a marine scale needs this kind of conformity. This article is general information, not legal advice: check requirements for your use with your national fisheries control authority and national metrology authority.

The two directives at a glance

	NAWI Directive 2014/31/EU	MID 2014/32/EU (Annex VIII, MI-006)
Covers	All non-automatic weighing instruments: an operator intervenes during weighing (Art. 1(1), 2(2))	Automatic weighing instruments: catchweighers, checkweighers, weight labellers, gravimetric fillers, totalisers, rail-weighbridges
When conformity is mandatory	Always, for the regulated uses in Art. 1(2)(a)-(f) (Art. 3(2))	Where a Member State prescribes the instrument for a measuring task (Art. 3, "optionality")
Marking	CE + M + year + notified body number (Arts 16-17)	CE + M + year + notified body number (Arts 21-22)
Conformity routes	B+D, B+F, D1 or F1 for simple mechanical instruments, or G (Art. 13)	For electronic systems or systems containing software: B+D, B+F, G or H1 (Annex VIII, Ch. I, point 4)
Replaced	Directive 2009/23/EC (Art. 45)	Directive 2004/22/EC

OIML R 76 and R 51 cover the same instrument types at international level; how they compare is explained in OIML R51 vs R76.

Regulated uses under the NAWI Directive

The NAWI Directive applies to every non-automatic weighing instrument, but its requirements bite when the instrument is used for one of six categories in Article 1(2) of Directive 2014/31/EU:

1. (a) determination of mass for commercial transactions;
2. (b) calculation of a toll, tariff, tax, bonus, penalty, remuneration, indemnity or similar payment;
3. (c) application of laws or regulations, or expert opinion in court proceedings;
4. (d) weighing patients in medicine;
5. (e) making up medicines and pharmacy or medical laboratory analyses;
6. (f) determination of price on the basis of mass for direct sales to the public, and the making-up of prepackages.

Member States must ensure that instruments are not put into service for uses (a)-(f) unless they meet the Directive, and that they continue to conform in use (Article 3(2)-(3)). Everything else is category (g). Instruments for category (g) carry only the manufacturer's name and Max and must not bear the Directive's conformity marking (Annex III, point 2). If a regulated instrument is connected to a device not used for regulated purposes, that device carries the restrictive use symbol: a black capital M on a red square of at least 25 mm, crossed by two diagonals (Article 6(5), Annex III point 3).

CE and M marking: what to look for on the data plate

Metrological conformity is shown by the CE marking followed by the supplementary metrology marking: a capital letter M and the last two digits of the year of affixing, in a rectangle as high as the CE marking. It is followed by the identification number of the notified body involved in production control (NAWI Articles 16-17; MID Articles 21-22). An instrument can be subject to several EU acts (NAWI Article 14(3)), so a CE mark without the M rectangle does not show metrological conformity.

A NAWI used for regulated purposes must also carry these inscriptions (Annex III, point 1.1):

• EU-type examination certificate number, where appropriate;
• manufacturer's name or trade mark, and type, batch or serial number;
• accuracy class in an oval;
• Max, Min and verification scale interval e, also shown near the display (point 1.4);
• where applicable: d, tare limits T = +/- , Lim and special temperature limits.

Without a manufacturer's specification, the temperature range is -10 °C to +40 °C (Annex I, point 7.2), relevant for open decks and freezer holds.

Notified bodies and certificates

A notified body is a conformity assessment body designated by a Member State to carry out the third-party tasks in the modules, such as EU-type examination (Module B) or unit verification (Module G). NMi in the Netherlands, for example, is notified body 0122 under both the MID and the NAWI Directive. When comparing scales, ask for:

1. the EU-type examination certificate and its scope, including accuracy class, temperature range and any conditions for use on moving platforms;
2. the EU declaration of conformity (NAWI Article 14);
3. evidence of the production-phase module and the notified body number on the instrument;
4. the sealing plan, showing which adjustments are secured.

For instruments whose performance depends on gravity, conformity assessment must take into account gravity at the place of use or a defined gravity zone (NAWI Annex II, points 7.1-7.2), a real issue for vessels that fish at very different latitudes, as explained in gravity, latitude and calibration.

What "legal for trade" means in the EU

"Legal for trade" is an informal term that EU law does not use. In EU terms it usually means three things together:

1. the instrument has passed conformity assessment under the NAWI Directive or, where prescribed, the MID, and carries CE, M and the notified body number;
2. it is used within the limits on its data plate and certificate (class, Min, Max, temperature);
3. it meets national in-service rules, such as periodic verification and intact seals, which WELMEC Guide 2 confirms are dealt with nationally.

A certificate for the type is not a guarantee that a specific installation is currently compliant: damage, broken seals or expired verification can change that. See calibration, verification and re-verification.

When is a conforming instrument required at sea?

Use on board or at landing	Likely NAWI/MID relevance	Who decides
Weights that set the price at first sale	Commercial transaction, NAWI Art. 1(2)(a)	National law; buyer and authority
Weighing under Article 60 of the Control Regulation	Systems must be "approved, calibrated and sealed in accordance with national law" (Reg. 2026/1932 Art. 5)	Fisheries control authority, under national law
Prepackages labelled with nominal quantity	Making-up of prepackages, NAWI Art. 1(2)(f)	National metrology authority
Automatic grading or checkweighing sold by weight	MID MI-006 if prescribed nationally (MID Art. 3)	Member State
Internal yield control, crew information, most research sampling	Typically category (g), not regulated	Operator; research protocols may still require traceable calibration

For the fisheries rules behind the second row, read EU Fisheries Control Regulation: weighing catches.

Motion, tilt and the essential requirements

NAWI Annex I, point 7.1 requires class II, III and IIII instruments liable to be used tilted to be sufficiently insensitive to the tilting that can occur in normal use. For automatic instruments, MID Annex VIII requires means to limit the effects of tilt, loading and rate of operation (Chapter I, point 3.1), and for instruments under special mechanical strain the manufacturer defines the mechanical conditions of use (point 1.3). WELMEC Guide 2:2023 section 2.3.1 translates this into test practice for NAWIs installed in ships, including acceleration compensation to at least ±3 m/s² and tilt tests up to 15°. Background on why this matters is in why ordinary scales fail at sea.

How WPL approaches this

WPL Industries holds NMi certificates EK-5417 and CE-284. Ask WPL which documents are available for the model and configuration you are considering, such as the M5 or M2, and confirm with your competent authority what your use requires. The legal metrology hub links all related guides.