Scales approved by Trading Standards for buying and selling precious metals, e.g. gold, silver, platinum, palladium




Read one article to find out everything you could possibly want to know about weighing and weighing machines: Choosing a Weighing Machine
see where you can buy other weighing machines:
small machines that weigh down to 1g or 0.1g or 0.01g or 0.001g

Also bench scales (battery-operated or mains-powered)
and also approved - the subject of this article.

Approved for use in trade means buying or selling on a value-for-weight basis. This applies to all transactions, whether in a shop, antiques fair, market or even a boot sale, even if you do not regard yourself as a trader. So if you are offering to buy or sell anything by weight, you MUST use an approved balance, it is the law; if you are not buying or selling by weight, then there is no need to read on.

These balances are Electronic Digital Weighing Machines (or scales), but I refer to them, in this article, simply as 'balances'.

I also refer to Weights & Measures Inspectors - these are Trading Standards Officers who happen to deal with weights and measures.


If you buy or sell by weight (i.e. an amount of money per gram or per ounce) then you need an approved balance. However, if you use a weighing machine as part of your valuation and stock control, but do not base the value on weight (e.g. jewellery where the main value is in gemstones, diamonds or antique value) then you do not need an approved balance - you are still a trader, but you are not using the balance 'in trade'.

Any Weights & Measures Inspector will notice if you are buying or selling by weight, even if you pretend otherwise. He will see that you are either calculating a price based on weight, or if, instead, you are calculating the price by carefully evaluating gemstones and hallmarks.

In the past I said that pawnbroking was an 'iffy' area, and that a few of our customers had telephoned their local Trading Standards merely to be told that this was an 'iffy' area. Following a 2½ hour meeting with a Weights and Measures Inspector, I can now clarify the position: pawnbrokers do need to use approved balances.

Another 'iffy' area is auctioneering. In theory, auction houses do not need to use approved balances, they are not buying or selling by weight, they are merely carrying out a valuation to set a reserve price. However, if they print the weight in their catalogue and if someone happens to be bidding on a weight basis, then the balance becomes 'for use in trade' and will need to be an approved balance.

At fairs and markets the same laws apply. Traders buying scrap must use an approved balance, it will be very obvious to any inspector that the buyer is testing, weighing and calculating a price per gram. An approved balance is not required for valuing antiques, weighing will be a small part of the valuation process, the buyer will not be buying by weight. You may say to yourself, “But nobody uses an approved balance in my market, and never has done!”. Maybe everyone unloading at the market parks on a double yellow line. I can only tell you about the law, not how it is enforced.


The actual standards for Weights and Measures are determined by the National Measurement Office who study the law, look at the science, and issue guidelines to Weights & Measures Authorities. The law is enforced by Weights and Measures Inspectors, they work for the Trading Standards department at your Local Council. You can find them by going to Trading Standard's Home Page (enter your postcode in the box at the top and click 'go'). If you wish to study the law yourself, see the Weights & Measures Act 1985 and its many amendments. Then, if you disagree with an inspector, you may accept the inspector's offer to have the matter decided in court.

Each Local Council's Trading Standards Department enforces the law at a local level. So whilst the law is consistent, each Local Council has its own priorities regarding enforcement.


First, the easy bit. A weighing machine used in trade must be stamped with a special sticker. These stickers are seals that are carefully placed over vital screws on the balance, if you break the seal and touch the screws (to open or recalibrate the balance) it will no longer be approved, have a look at the marks (pdf).

There are four Classes (grades) of approved balance:

CLASS 4 need not concern you, it is for heavy items such as heavy goods vehicles
CLASS 3 is for general goods, from light-ish (e.g. herbs) to heavy-ish (bags of fruit)
CLASS 2 is for items that have a high value per gram, specifically precious metals
CLASS 1 need not concern you, it is for scientific applications, e.g. for weighing down to 0.0001g


- Complication No. 1: 1g or 0.1g or 0.01g?

When you buy an approved CLASS 2 balance the manufacturers might give you its specification as, for instance, 6000g in steps of 0.1g. What they don't tell you is that once it's approved, you are not supposed to use that last decimal place when used ‘in trade’. So, for instance, having spent hundreds of pounds and thinking you will be weighing down to 0.1g you will discover that the balance now has a red cross painted over that last decimal place so that it only reads to the nearest 1g. (though the 0.1g will still be visible under the red cross). For your own purposes (away from customers and merely for your own valuation purposes) you may weigh to 0.1g, but when buying by weight you are supposed to ignore the 0.1g and work to the nearest 1g.

All the balances we sell have this two-tier system, a more sensitive reading for your own use and a less sensitive reading for buying precious metals by weight.

- Complication No. 2: buying or selling?

If you are selling by weight, the customer must be able to see the display and you must never use a balance with a ‘crossed out’ digit, but you can use it to price items by weight (ignoring that ‘crossed out digit’) out of sight of the customer.

The A&D balances do not have a display facing the customer, therefore they can be used for buying by weight but not for selling by weight. The OHAUS scales have an optional front-facing display with which you can sell by weight in addition to buying by weight.

- Complication No. 3: balances calibrated by area

The cheaper CLASS 2 balances (£299.00 to £499.00) are calibrated for a particular area (usually a town, sometimes a full postcode). This is to allow for variations in gravity (which varies according to latitude and altitude). So if, for instance, you use a balance in Liverpool, then it will be calibrated for Liverpool. This means that if you work at fairs and markets all over the county you should have a weighing balance for each location. And you cannot recalibrate them, they are fixed (with a seal) to make sure you can't recalibrate them.

So what happens when a Weights & Measure Inspector visits?

If you show him the Certificate of Calibration, and the town (or postcode) is not where you are actually using the balance, then he will tell you to stop using it. If you can’t find the certificate, the inspector could ask the supplier where the balance was calibrated then get the details from the laboratory. However, it is more likely that he will simply test the balance, and if it is OK it is OK and everybody is happy. However, the point about them being calibrated for use in a particular area is that you don’t know if it can be used in another area – gravity in two locations a hundred miles apart might be the same, or might be different in two neighbouring villages.

- So which one?!

At this point, customers say to me, in exasperation, "Just tell me which balance I need that is OK according to the law, and which I can carry around the country!". The answer is the more expensive Class 2 balances (£495.00 and £595.00). These are not calibrated for a particular area, they can be used anywhere. HOW this works is quite ingenious. You calibrate it by pressing a button, and then you can hear motors whirring as they lower an actual physical weight onto an internal weighing pan to reset the electronics to match the weight (i.e. calibrate it).


With a cheaper balance (calibrated for use at one location) check it whenever it is moved. If you work at fairs and markets, that includes moving to a new venue, it also includes moving the balance from one side of the stall to the other. Even if the balance lives on a shop counter and is never moved (not even by a few inches) it is wise to check it every few weeks. To check it, buy a weight, any weight that is near (or at) the top of the balance’s range. Switch the balance on, place the weight on the platform, check the reading. It really is no more complicated than that. Although the instruction manual will tell you how to recalibrate the balance if you are getting incorrect readings, you cannot do this – this feature is disabled when the balance is approved, you must send it back to us for recalibration. There's a 2-page booklet you can download, the first page is about DIY calibration of non-approved scales, see page 2 for details of when an approved scale might need to be recalibrated.

An approved balance is not likely to need recalibrating from one year to the next unless it is mis-treated. Do not overload it, do not allow anyone to ‘bounce their hand’ on it. If transported, do not pack it with any pressure on the weighing platform. Do not store anything on the weighing platform, not even a pen or a receipt book. An approved balance is expensive, look after it!

With a more expensive (self-calibrating) balance, there is no ‘checking’ to be done, you simply press the button for ‘recalibrate’. Some balances automatically recalibrate themselves (or ask you to press the button) if they have not been used for a few hours or if the temperature changes suddenly. As explained above, these balances are expensive, do not overload them, they are very sensitive.


You cannot recalibrate approved scales yourself, this feature (often listed in the instruction manual) is disabled when the balance is calibrated by Trading Standards (‘approved’). You must send the scale back to us, the charge is about £150.00. This is not to be confused with the machine being ‘broken’. If it is broken, it will need to be repaired, and once it is repaired it will need to be calibrated again.

Trading Standards charge for calibration quite independently of any “repair” and the fee is not refundable. If it fails, you have a choice. We can return it to you un-repaired (you don’t get the calibration fee back) or we can quote for a repair. Not only don’t you get the original calibration fee back, but the quote for the repair will include another calibration fee…because Trading Standards are going to charge again. I think this is grossly unfair but please understand - we do not make the rules. The best I can do is to give you an idea of what might be wrong with the scales in the first place:

• It isn’t weighing accurately when you weigh an item at the top of its range (e.g. when you weigh a 200g weight on a machine that weighs up to 200g).

- Providing the error is only slight, recalibration should fix it.

• It weighs perfectly but you haven’t had it checked for a long time.
- There’s no harm in getting it recalibrated. In laboratories scales are recalibrated every year. Most shopkeepers wait until their scale is giving incorrect readings before getting it recalibrated. My advice is to check it regularly (by weighing known weights) and get it recalibrated the moment it gives an inaccurate reading. If you’re lucky, it will be fine for three or four years, if you’re unlucky it might need recalibrating after one or two years. Nothing remains perfect forever, it will eventually need recalibrating.

• It is dead, the display won’t light up.
- Sounds like a power problem. Check the power supply (mains adaptor) to make sure it works, it should get warm in use. Check that you are using the correct power supply, not to weak (it won’t power the machine), not to powerful (you will burn out the electronics). If you return the machine to us, you must include the power supply that you have been using with it.

• The reading is erratic, it drifts (or jumps) up and down when nothing is being weighed.
- There’s a high probability that the machine has been dropped or overloaded. e.g. if someone ‘bounces’ their hand on the weighing platform, just to see what happens, or if something far too heavy has been weighed, or if It’s been crushed in transit. You have probably destroyed the strain gauge (the sensor at the heart of the machine) and, if so, it is beyond repair.

QUICKTEST, Watford, WD18 8PH, Tel. 01923 220206, email info(at)