[Home](/)/[Resources](/resources)/UK Measuring Instruments Measuring InstrumentsMID / NAWI # UK Measuring Instruments Regulations Guide The Measuring Instruments Regulations 2016 and Non-Automatic Weighing Instruments Regulations 2016 govern measuring instruments used for legal purposes in Great Britain. These regulations ensure measurement accuracy and reliability through conformity assessment and UKCA marking. Copy Link[Share on WhatsApp](https://wa.me/?text=https%3A%2F%2Fkrono-labs.com%2Fguides%2Fuk-measuring-instruments) ## MID instrument types Water metersMeasurement of cold and hot water consumption Gas metersMeasurement of natural gas volume Electrical energy metersMeasurement of active electrical energy Thermal energy metersMeasurement of heat in heating systems Measuring systemsLiquid fuel and other liquid products measurement Automatic weighing instrumentsContinuous weighing and bulk measurement TaximetersFare calculation in taxis Material measuresLength, area, volume measurement ## NAWI accuracy classes Class Accuracy Verification error Typical use I Special precision ±0.5e to ±1.5e Laboratory, precious metal weighing II Precision ±1e to ±3e Laboratory, pharmacy, industrial III Medium precision ±2e to ±6e Commercial, industrial weighing IIII Ordinary precision ±5e to ±15e Simple weighing applications ## Conformity assessment Measuring instruments typically require third-party conformity assessment by a UK Approved Body. The assessment process includes: * **Type examination (Module B):** Assessment of design and testing to verify compliance with essential requirements * **Quality system approval:** Evaluation of manufacturer's quality management system for production control * **Surveillance:** Ongoing monitoring of production to ensure continued conformity * **Verification:** Individual instrument testing before first use in legal metrology applications After conformity assessment, the instrument receives UKCA marking and an identification number of the Approved Body. For MID instruments, the M mark may also be used. ## Learn this properly, not just for one product In-depth courses and books that teach the process — not a one-off answer you'll need to look up again next time. [Start the course — $149](/courses/09-ukca-marking-for-electronics-products)See your free roadmap [Prefer to read? Get the book — $24.99](/books/09-ukca-marking-for-electronics-products) ## Frequently asked questions ### What is the difference between MID and NAWI? MID (Measuring Instruments Directive) covers instruments used for legal measurement in specific applications like utility meters, fuel dispensers, and taximeters. NAWI (Non-Automatic Weighing Instruments) covers weighing instruments used for commercial transactions, law enforcement, and regulated applications. ### Do measuring instruments need UKCA marking? Yes, measuring instruments within scope of the Measuring Instruments Regulations 2016 and Non-Automatic Weighing Instruments Regulations 2016 require UKCA marking when placed on the GB market. They must undergo conformity assessment based on their accuracy class or type. ### Is Approved Body involvement required? Most MID and NAWI instruments require third-party conformity assessment by a UK Approved Body. The assessment includes type examination, quality system evaluation, and ongoing surveillance depending on the conformity assessment module. 🇬🇧 UK roadmap for your product Every standard, document, and test that applies — free, no account required. See your free roadmap[ Want an expert to take your product through 🇬🇧 UK compliance for you? One consultant from Krono's compliance team takes your product from requirements to legal sale, with a fixed quote before any work starts. See compliance services](/services) Learn this properly In-depth course that teaches the full process, not just this one answer. [Start the course — $149](/courses/09-ukca-marking-for-electronics-products)[Prefer to read? Get the book — $24.99](/books/09-ukca-marking-for-electronics-products) Related guides * [UKCA Marking OverviewComplete guide to UKCA marking for the Great Britain market: requirements, timeline, costs, GB vs NI differences, and how to tr…](/guides/ukca-marking) * [UK Testing and Approved BodiesComplete guide to UK testing requirements, UK Approved Bodies (formerly Notified Bodies), UKAS accreditation, and selecting lab…](/guides/uk-testing-approved-bodies) * [UK EMC ComplianceComplete guide to UK Electromagnetic Compatibility Regulations: EMC testing requirements, designated standards, UKCA marking, a…](/guides/uk-emc-compliance) Educational resource only. Measuring instruments for legal use require strict compliance. Always consult an Approved Body for conformity assessment.