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What is a Trade Approved Scale? (Complete Guide)

What is a Trade Approved Scale and why should you be using one?

For many applications, using a Trade Approved scale is a legal requirement.

For many businesses that use weighing scales, however, what a Trade Approved scale is is a bit of a mystery.

In this blog post, we explain what a Trade Approved scale is, why it’s different to a standard weighing scale, and when you should be using one.

What is a Trade Approved scale?

Trade Approved scales must be used in order to comply with regulations for buying and selling goods by weight; they are also referred to as verified scales, legal for trade scales and stamped scales. In order to receive their 'Trade Approved' certification, weighing scales must undergo rigorous testing.

The amount of testing required to ensure a scale is approved, should also mean there is no discrepancy between weight readings - two different scales weighing the same item should give the same weight.

Weights & Measures legislation has required the use of approved scales for over one hundred years. The legislation is in place to protect the customer as well as the seller.

The best way to think of it is: If money is going to change hands as a direct result of the reading on a weighing scale, legally, the weighing scale must be Trade Approved.

What is a Class III Approved Scale?

Class III Approved is another word for Trade Approved that is most commonly used in a medical context.

Class III scales are strongly recommended when calculating prescriptions or monitoring health signs, and specific accuracies of scale need to be used for certain medical tasks.



When must a scale be Trade Approved?

The NAWI Directive defines six applications that require the use of a Trade Approved weighing scale:

  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.



Where are Trade Approved scales typically used?

Trade Approved scales should be used, for example, in the following environments:

Shop scales

When weighing fruit and vegetables in a grocery store and using the weight reading to determine the price. An example is the DS-781SS Retail Scale used by Macsorsons Fishmongers.

Trade Approved scales are also often used at market stalls, where sellers weigh out meat, fish, soaps, sweets and more and sell them based on the overall weight.

Bottling processes

If your bottles specifically states the volume of the bottle and the price is based on this volume, then a Trade Approved scale must be used.

Container Weighing

Weighing containers for loading onto a ship: as part of the SOLAS container weight regulations which require a verified proof of weight.

Business to business sales

If the business buys and sells a good based on its weight - such as a scrap metal dealer buying metals based on weight - Trade Approved scales are required. Other examples include recycling and waste management businesses (like Global Recycling, who use a Marsden Platform Scale to weigh confidential waste).

Industries where Trade Approved scales are suitable include food, alcohol, firewood or logs, liquid fuel, landscaping materials, precious metals and mechanical parts.



Who approves a Trade Approved scale?

The UK Weighing Federation’s Ian Turner told Marsden: “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."

They have strict guidelines that the scale will need to conform to - this will include everything from accuracy of the reading to whether interference from other devices causes the display to show an incorrect reading.

“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 instruments. All of these detailed checks ensure that both consumers and traders can be assured that the basis of their transaction is fair and just.”

Once tested and verified, the scale will then be issued with a Declaration of Conformity. If you buy a Trade Approved scale, it should come with a Declaration of Conformity as evidence of it having gone through this testing process.



How do we make sure our scales are Trade Approved?

Making a scale Trade Approved can be a complicated process to ensure the scale has this level of accuracy and reliability. But with the help of Marsden technical support, we’ve created a simplified explanation of the process below.

It begins with a process known as ‘compatibility in module’ where the loadcells are tested against the indicator.

“We’ll know in advance whether a scale is Approved, as approval documents are provided - parts such as the loadcells will come with Trade Approved status,” said Marsden’s Steve Rayner.

The scale is then put together by the highly-skilled Marsden team, recalibrated and verified.

“Ensuring the scale is weighing accurately enough comes as part of the verification and reverification process,” said Steve. “The scale will have to meet certain tolerances and these are very tight.”

Approved weights are put on the scale to a tenth of a division. This means that if a scale has graduations to the nearest 100g, Marsden puts on weights of 10g at a time, and ensures the scale clicks over at the point the tenth weight is added. First this is done in the centre of the scale, but then the corners of the scale are subject to the same process.

(Below: EC Type-Approval certificate, which states the manufacturer's name, that the scale is Class III Approved, the capabilities of scale and other information).

EC Type-Approval Certificate



What should be done if you need Trade Approved scales?

Many businesses, if they are not aware already that they need to use Trade Approved scales find out during a visit from Trading Standards (or the equivalent bodes outside of the UK). Typically, when Trading Standards identify an unsuitable scale being used for a Trade Approved application, they give the business a set number of days to replace the scale.

It is then that customers will usually contact Marsden for advice and to place an order. Almost every Marsden product is available with next day delivery, meaning the downtime the business will experience is minimal.



But how do you know which Trade Approved scale is the right one for your application?

Different Trade Approved scales are suitable for different needs. For example, if you are bulk weighing items for pricing then a platform scale may be more suitable - such as the this mild steel platform scale, with a Trade Approved indicator.

If space is limited in a warehouse or factory environment, then a Trade Approved pit mounted scale is ideal as it sits flush to the factory floor.

For weighing small items, which require a fine graduations, then choose a bench scale like the Jadever JWN.


A buyer's guide of our Trade Approved scales can be found here. For more information about any of our scales, call 01709 364296 or contact us here.