In the guide
Weighing equipment that is used for legal and trading purposes is required to be accurate and appropriate for its purpose
This guidance is for England, Scotland and Wales
Weights and measures (also known as 'legal metrology') legislation enforced by trading standards services places requirements on weighing equipment for use when goods are bought, sold or produced. It covers weighing equipment that determines the final quantity of goods delivered to customers.
The legislation also applies to equipment used for weighing patients for the purpose of medical monitoring, diagnosis and treatment as well as weighing equipment used for making up medicines on prescription in pharmacies and determination of mass in analyses carried out in medical and pharmaceutical laboratories.
There are also other particular weighing applications where this legislation applies, which include the calculation of tolls, tariffs, taxes, bonuses, penalties, etc based on weight, expert opinions given in court proceedings concerning weights and the application of laws.
Weighing equipment used during a production process (for example, to determine the weight of ingredients) does not need to comply with this legislation, neither do check scales for consumers' use in supermarkets etc, provided there is a further final weight check over an authorised, accurate and correctly marked weighing machine.
Equipment types, uses and construction
The controls over weighing equipment depend on its type of construction and the use to which it is put. All weighing equipment that this legislation applies to must be suitable for its intended purpose in terms of its construction, weighing capacity and level of accuracy; it must indicate weight correctly to within defined limits.
Weighing equipment can be either:
Weighing machines for legal use have to be constructed to a particular Government or European Union (EU) specification and bear particular conformity markings, stamps, stickers or other indications to show that the equipment complies with these requirements. The required indications have changed over the years and examples of them are outlined later in this guide.
Additionally, weights that are used in conjunction with weighing equipment must be correctly constructed and bear particular indications to show that they are suitable for legal use.
When considering using any weighing equipment for legal use it is recommended that the assistance of your local trading standards service be sought; they will be able to advise on the suitability of equipment.
Construction, type approval and verification
Weighing equipment used for legal purposes must be accurate and manufactured in accordance with an approved type approval or examination certificate.
Weighing instruments are either:
The crown stamp, qualifier's identification stickers and other markings
When weighing equipment for legal use has been made and qualified as conforming to all manufacturing and accuracy requirements the required stamps, stickers and other indications are attached to it by the manufacturer or approved qualifier. Some equipment - weighbridges, for example - is required to be tested and have its final approval stamps applied when the equipment has been installed in its place of use.
The following examples of stamps and stickers may be found on weighing equipment that has been approved for legal use:
|The crown stamp, year of application and official number of the inspector of weights and measures who passed the equipment as fit for trade use is found on a lead plug embedded into older, traditional weighing equipment.|
|The M sticker indicates that the equipment it is attached to has been manufactured in accordance with legal metrology requirements.
On newer equipment the M symbol will have the year of manufacture attached.
|Thenotified body sticker indicates which organisation examined and approved the equipment as being in accordance with all manufacturing and accuracy requirements.|
|The requalification sticker indicates that the equipment has been repaired or adjusted since it was manufactured to maintain manufacturing and accuracy requirements.|
|The CE mark, which indicates that the equipment has been manufactured in accordance with all relevant EUlegislation (low voltage electromagnetic compatibility, restriction on hazardous substances, etc) and the year of manufacture.
On newer equipment the year marking will be omitted if it is attached to the M symbol.
As can be seen, the appearance of these stickers has changed as legislation has developed and been subjected to amendments over the years, with more changes being introduced as new requirements are introduced. When considering the purchase of new or used weighing equipment the stickers and stamps may not be exactly as illustrated above due to these ongoing changes. Your local trading standards service will, however, be able to advise on the current stamp and sticker requirements for particular equipment.
Approved weighing equipment is also required to bear various other indications relating to the weighing capacity, accuracy, etc as detailed on the approval certification, with more modern equipment having the required information on an attached 'data plate' or tamper-proof label. The data plateor tamper-proof label, as typically illustrated below, may also have the required stickers attached so that all required information is contained on theinstrument in one easily discernible position.Newer equipment may also have the manufacturer's or importer's name, address and trade mark displayed on the data plate as well as additional information relating to different tare intervals, safe loads, operational temperatures, etc. The data plate also commonly includes information relating to electrical rating, power consumption, etc.
Alternatively, the requirements allow some of the required markings to be displayed simultaneously on the equipment's display screen.
The accuracy of approved weighing equipment is divided into four classes and careful consideration must be given to which accuracy class should be used for particular weight determination.
|Use||precious metals, precious stones, pharmaceutical purposes, etc||general weighing purposes||ballast and other building materials, waste disposal and recycling purposes|
As there have been many changes to the legislation relating to the construction, markingand use of weighing equipmentfor legal use you should seek advice from your local trading standards service when consideringthe purchase and use of weighing equipment, especiallyin relation to second-hand equipment.
Weighing equipment that has been rejected for legal use
When considering the purchase and use of second-hand weighing equipment for trade purposes, one stamp or sticker to look out for is the six-pointed star.
The six-pointed star stamp or sticker is applied to approved equipment that has been 'rejected' as it was found on inspection to be inaccurate or not in compliance with manufacturing requirements; it also indicates that the equipment has not since been adjusted or repaired.
It is an offence to use weighing equipment bearing a six-pointed star indication for legal purposes.
It may be possible for 'rejected' weighing equipment to be adjusted or otherwise repaired and submitted to the appropriate body for requalification.
Automatic weighing equipment
Automatic weighing machines are capable of determining or checking the weight of items without the intervention of an operator and are usually used in specialised circumstances within a production process. Their approval requirements and usage circumstances are different to non-automatic equipment and more detailed advice concerning their suitability for use can be obtained from your local trading standards service.
Weights that are required to be used in conjunction with approved weighing equipment must bear an indication that they are sufficiently accurate and have been manufactured in accordance with legal requirements.
The indication will normally be found stamped into a lead plug in the base of the weight and take the form of the traditional crown stamp or EU mark of approval.
As with weighing equipment, any weights that bear a six-pointed star stamp were found to be inaccurate when they were last inspected and would be illegal for use for legal weighing purposes.
Maintenance and use of weighing equipment
Weighing equipment can give incorrect readings because of poor practice or misuse and the following points should be noted to ensure continued accuracy:
Failure to comply with trading standards law can lead to enforcement action and to sanctions, which may include a fine and/or imprisonment. For more information please see 'Trading standards: powers, enforcement and penalties'.
Last reviewed / updated: February 2020
In this update
No major changes
This information is intended for guidance; only the courts can give an authoritative interpretation of the law.
The guide's 'Key legislation' links may only show the original version of the legislation, although some amending legislation is linked to separately where it is directly related to the content of a guide. Information on amendments to legislation can be found on each link's 'More Resources' tab.
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