Trade Approved Scales

What is a Trade Approved scale?

A Trade Approved scale is a weighing scale that is approved for use when an item is being priced based on its weight. In many countries, including the UK, Trade Approved weighing scales must by law be used for this purpose.

A Trade Approved scale undergoes far more testing than a non approved scale – in fact, during type approval testing, the scale will undergo a huge number of tests for accuracy and reliability in weighing.

Trade Approved scales may also be referred to as verified scales, legal for trade scales and stamped scales. Trade Approved scales carry an ‘M’ (for ‘metrology’) logo on their dataplate.


Why must a Trade Approved scale be used?

Weights & Measures legislation has required the use of Trade Approved scales in trading for over a century. The legislation, which today is the Weights & Measures Act 1985, is in place to protect the customer as well as the seller. It ensures that the correct price for an item or items is quoted when that price has been based on the weight reading.

It also means that all scales used for such purposes are all tested to the same standard so that there should be no discrepancy between readings should two different scales be used to weigh the same item to determine its price.


When must a Trade Approved scale be used?

The Non-Automatic Weighing Instruments (NAWI) Directive, and the UK Regulations that implement this directive, defines six applications that require the use of a Trade Approved weighing scale. These are listed in Article 1.2(a) of the Directive:

1. Determination of mass for commercial transactions

2. Determination of mass for the calculation of a toll, tariff, tax, bonus, penalty, remuneration, indemnity or similar type of payment

3. Determination of mass for the application of laws or regulations; expert opinion given in court proceedings

4. Determination of mass in the practice of medicine for weighing patients for the purposes of monitoring, diagnosis and medical treatment

5. Determination of mass for making up medicines on prescription in a pharmacy and determination of mass in analyses carried out in medical and pharmaceutical laboratories

6. Determination of price on the basis of mass for the purposes of direct sales to the public and the making-up of pre-packages.

Examples of when Trade Approved scales should be used include:

1. Shop scales. Weighing fruit and vegetables in a grocery store, and using the weight reading to determine the price

2. Bottling processes. Filling beer bottles that specifically state the volume of contents of the bottle – and the price is based on how much content there is in the bottle/the size of the bottle

3. Weighing containers for loading onto a ship in order to obtain a verified proof of weight (as part of the SOLAS container weighing regulations)

4. Business to business sales. For example, a scrap metal dealer, who buys and sells metal based on its weight, would need to use trade approved scales. Likewise, recycling and waste management businesses are required to use trade approved scales.

A typical visit from Trading Standards will include checking weighing scales for compliance with the Weights & Measures Act 1985.


Who approves a Trade Approved scale?

Accredited laboratories, known as Notified Bodies, carry out all of the tests that the scale is subject to when undergoing approval. They will be based in a range of European countries and will all be accredited to the same international standards to ensure that there is a consistency of results.

Once the design of the scale is approved, and it has been put into production, an approved verifier must then check each one before it can be used for any of the six applications listed above. These tests will cover both the accuracy and the repeatability (providing consistently accurate weight readings) of the instrument. All of these detailed checks ensure that both consumers and traders can be assured that the basis of their transaction is fair and just.

Traditionally, the verifier would ‘stamp’ the scale to show that it was Approved. Today, all the information can be found on the scale’s dataplate.


Where can I find out more?

If you are unsure whether or not you need to use a Trade Approved scale, speak to the Marsden team. We are able to advise on whether you should be using stamped scales, and we can also direct you to the most appropriate scales for your application. You can speak to us on 01709 364296.

If you need more clarification on the legal requirements and the legislation in the UK, the UK Weighing Federation can be contacted on 01727 582015.

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