NMO Technical Services

Product certification, quality management system certification, pre-assessment, and standards calibration.

Product certification, quality management system certification, pre-assessment, and standards calibration

Manufacturers can draw on our specialised conformity assessment services to enable them to place regulated weighing and measuring instruments on the market. These include items as diverse as beer glasses, fuel dispensers, precision balances, railway weighbridges, supermarket scales, taximeters and utility meters.

Within Europe, the Measuring Instruments Directive and the Non-automatic Weighing Instruments (NAWI) Directive supply the legal framework for conformity assessment. Both are transposed into UK law.

Outside Europe, recommendations for specific weighing and measuring instruments are produced by the International Organisation for Legal Metrology (OIML).

Our client services

NMO Technical Services – part of the Office for Product Safety and Standards (OPSS) – offers two main types of conformity assessment:

  • Product certification, sometimes called type examination, involves the rigorous testing of instruments at the design stage to ensure they comply with the regulations
  • Quality management system certification is the approval of your process for producing an instrument, or verifying it following its repair or modification

We also provide:

Standard terms and conditions for sale of goods and services (PDF, 101KB, 4 pages)

Our accreditations

Our accreditations are external endorsements of our work. NMO is:

UKAS accreditation

NMO’s calibration, testing, ACB and type approval services are accredited by the UK Accreditation Service (UKAS). The scope of NMO’s accredited services is clarified in certificates that can be found by searching for ‘NMO’ on the UKAS website.

  • Calibration – UKAS reference number 0205
  • Testing – UKAS reference number 0004
  • Quality management system certification – UKAS reference number 0135
  • Product certification – UKAS reference number 0135

We are also responsible for national type approval and verification of certain instruments under the Weights and Measures Act 1985.

Our remit

Conformity assessment under the Measuring Instruments and NAWI Directives (PDF, 117KB, 1 page)

Certification under the Measuring Instruments and NAWI Directives (PDF, 251KB, 2 pages)

UK national type approval (PDF, 400KB, 1 page)

OIML certification (PDF, 200KB, 1 page)

Our facilities

The equipment in the laboratories and chambers at our Teddington site is all fully traceable to national standards, operated in accordance with ISO/IEC 17025:2017, and available for research or pre-assessment testing.

NMO testing facilities

We liaise closely with the legal metrology team in OPSS, whose guidance on the Weights and Measures Act 1985 and related matters will be relevant to many of our existing and potential customers. This extends to training and consultancy.

National regulation: Weights and Measures

Certificates issued by NMO

Measuring Instruments Directive (2004/22/EC and 2014/32/EU)

NAWI Directive (2009/23/EC and 2014/31/EU)

EEC type examination

UK national type approval

EEC certificates issued under Directives revoked by the Measuring Instruments Directive continue to be valid until their date of expiry but cannot be renewed.


We are currently in the process of updating our Guide to certification services.

Includes technical annexes on:

  • automatic weighing instruments
  • non-automatic weighing instruments
  • liquids other than water
  • cubic measures
  • intoxicating liquor measuring equipment and capacity serving / transfer measure equipment
  • material measure of length
  • water meter certification
  • taximeters
  • thermal energy meters
  • gas meter and volume conversion devices certification
  • active electrical energy meters certification
  • dimensional measuring instruments

Information on OIML approvals

Weights and measures technical updates

Contact for further information

Head of NMO

Impartiality committee

The impartiality committee ensures that policies, practices and operations are in accordance with ISO 17021:2015-1 and ISO 17065:2012 and all guidance relating to these two standards issued by the International Accreditation Forum and NMO accreditation bodies.

The committee comprises a minimum of 4 people and is elected by the Leadership Team of OPSS. The chair and at least 2 other people are not NMO personnel. NMO is represented by the Quality Manager, or his or her deputy. The membership is selected to ensure no single interest predominates. Internal and external NMO personnel are considered to constitute a single interest and so must be balanced by other interests.

The role of the committee is to:

  • assist in developing the policies relating to the impartiality of the certification activities of NMO
  • counteract any tendency to allow commercial or other considerations to prevent the consistent objective provision of certification activities

The committee advises on matters affecting confidence in certification, including openness and public perception, and conducts a review, at least once annually, of the impartiality of the audit, certification and decision-making processes of NMO.


Should you wish to make a complaint about the product or management system certification services we provide, write to:

Head of Quality


  • explain your complaint and any related issues
  • provide examples or supporting evidence where possible
  • describe the action you would like us to take to resolve matters

Process overview

  1. Acknowledgement – All complaints will be acknowledged within 2 working days, but we aim to acknowledge them immediately.
  2. Investigation – The Quality Manager will ensure a full investigation is carried out, the level of which will be commensurate with the frequency of occurrence and severity of the complaint.
  3. Response – Once the investigation has concluded, we will address the complaint by taking the necessary action.
  4. Communication – The decision in relation to the complaint will be documented, recorded, and sent to the complainant within 10 working days from the acknowledgment of the complaint.


Should you wish to appeal against a technical or certification decision we have made in relation to product or management system certification, write to:

Head of Quality

Appeals may be made, for example, against our decisions to refuse or suspend certification for an instrument or management system, or in relation to the grading or validity of non-conformities.

Your appeal will be acknowledged within 2 working days. If deemed valid, it will be reviewed and a decision communicated to you within 10 working days from the acknowledgment of your appeal. A robust explanation for our decision will be included.

Health and safety

OPSS recognises that the work of NMO contains hazards relating to its laboratory-based activities and for that reason is committed to achieving certification of its approach to managing those hazards through the British Standard for Occupational Health and Safety BS ISO 45001:2018.

NMO health and safety policy and objectives (PDF, 28.8KB, 1 page)

Published 2 April 2014
Last updated 19 March 2018 + show all updates
  1. Page content revised, now including links to dedicated pages on product certification, quality management system certification, pre-assessment, and standards calibration.

  2. The Guide to Certification Services has been updated to version 3.

  3. Video added introducing NMO Certification and Technical Services.

  4. The document "A guide to NMRO Certification Services" has been updated to revision 2 and is now called "A guide to NMO Certification Services" dated (27 July 2017).

  5. Addition of a guidance publication relating to the activities of the NMRO Certification Services, and link to weights and measures technical updates.

  6. Addition of information regarding the complaints and appeals processes

  7. Amended to include information on management system certification marks and restrictions of use.

  8. This Guide has been updated to include a link to Legal metrology training: support of national competency for UK trading standards officers, and international consultancy services

  9. First published.