WEIGHING MACHINES

To see all weighing machines (and to buy)
(or to return to all weighing machines if you clicked on a link there)
click here

Scroll down or click here to go directly to the BUYING GUIDE

Click here to find out about APPROVED BALANCES

CAPACITY AND RESOLUTION

The readability (resolution) is the finest weight the digital display (or the scale on a spring balance) will show, the capacity is the maximum weight. Some models read down to ('have a resolution of") 0.001g, some models read down to ("have a resolution of") 100g...and anything in between. The resolution most-used in the jewellery and antiques trades is 0.1g (and the capacity anywhere from 150g to 2000g)

Some people get confused with decimal points, e.g. 0.001g, 0.01g, 0.1g etc. Before ordering please do think for just a second:

0.01g = a diamond (though diamond dealers need a resolution of 0.001g for accurate pricing)
0.1g = a couple of matches (though it depends on the size of the match)
1g = two or three small paperclips
10g = a one pound coin (actually 9.5g)
100g = nearly half a pack of butter, a large chocolate bar (not the 'giant' bars)
1000g = a small bag of sugar or two medium packs of pasta

APPLICATIONS (the prices in this section updated in July 2010)

0.001g is for the accurate pricing of diamonds (typcial resolution in carats, 0.01ct = 1pt)
The capacity of these balances is usually 10g or 20g.

0.01g.resolution is OK for weighing gemstones and diamonds approximately (typical resolution in carats is 0.05ct = 5 points), and is good for powder for ammunition (weighed in grains, approx. 15 gr = 1g).

0.1g. resolution is best for gold and platinum, rare coins, model-aircraft parts, catalysts for adhesives, photographic chemicals. 0.1g of 9ct gold is worth about 95p (that's the actual gold value, you won't get this much selling scrap).

20g, 50g (or even 100g) resolution is good for heavy silver items, large parcels, suitcases etc. The capacity of these balances varies from 2.5Kg to 30Kg (80oz Troy to 950oz Troy). 1oz (31g) of silver is worth about £11.00 (that's the actual silver value, you won't get this much selling scrap).

WEIGHTS

There are two ounces. The Ounce Avoirdupois (often called the "English Ounce") = 28g and is for weighing food and goods; the Troy Ounce, ozt = 31.1g and is for weighing gold and silver. The Pennyweight (20 dwt = ozt) was discontinued in the U.K. over 30 years ago but is still used in primitive countries such as the U.S.A. The sub-division of the pennyweight was the grain (gr, originally based on a grain of wheat) and is still used for weighing powder for ammunition. A carat (metric carat) is 0.2g, used for weighing diamonds (divided into 100 points, pts) - not to be confused with carat as a measure of purity (spelt Karat in the U.S.A.). Have you seen our conversion charts?

MECHANICAL OR DIGITAL?

Mechanical balances with springs (spring balances) are out of fashion, people tend to think that any machine with batteries and an LCD display must be accurate, and anything purely mechanical isn't so accurate. Not true, a good quality spring balance is every bit as accurate as a digital balance (see below for definition of 'accuracy'). The high precision PESOLA spring balances are smaller (thin and long) than any digital balance, battery-free, difficult to overload, survive being dropped. 

Spring balances are the best choice for hanging (with a clip or a hook) letters and small packets, or bulky items such as silver teapots or bags of silver scrap.

The pocket-size digital balances are best for tiny object such as rings, earrings, rare coins, especially if you intend to carry it around. The larger, table balances, should be chosen for fixed use on a workbench or table. Both are available in a large range of resolutions and capacities.

WEIGHING AND THE LAW 

If you buy or sell on a weight-for-value basis you must, by law, use an approved balance. "Approved" means approved by Trading Standards. We do sell approved digital balances. An approved balance must be use whether selling (or buying) in a shop, antiques fair, street market, boot sale or even from home. It does not apply to Auction Houses because, technically, they are not 'buying and selling."

TECHNICAL STUFF

- Names

If it is a tube with a spring we call it a spring balance. One variation is a 'digital spring balance' - you hang the item on the hook and read a digital display (it works by deforming plates of metal rather than stretching a spring, but the principle is the same). Another variation is a semi-circle of metal with a hook and a loop (no springs). A good name to describe all these is 'hanging balance'.

If it is flat-ish and has a battery and a digital readout and sits on a table (many are small enough to fit in a pocket too) we call it a digital (or electronic) balance.

Technically-speaking none of the above are 'balances' at all, it is only a balance if you 'balance' the goods against weights, e.g. two weighing pans balance over or under a beam (a beam balance)...which we don't sell.

The accuracy of a beam balance depends purely on the accuracy of the weights; the accuracy of a spring balance depends on the quality of the spring; the accuracy of a digital scale depends on many factors including the quality of the strain gauge (weighing element), the temperature and variations in gravity.

- Readability and accuracy

Put a 10g. weight on two digital scales, you might get two different readings, both have the same readability (resolution) but one might be more accurate than the other. Nothing is 100% accurate.

Accuracy is measured in 'percentage'. Multiply the percentage by the weight (any weight you like, any weight you are likely to weigh) to calculate the possible error. I've never been able to find out the percentage accuracy of the miniature digital scales used in the antiques trade, but from my experience of manufacturing them many years ago, I would guess it's about 0.2%.

An example. You weigh 10g, the calculation is 10 X 0.002 = 0.02g possible error. On a scale that weighs to the nearest 0.1g. you would never notice an error of 0.02g. But now try a heavier weight and you will see that the error is significant, e.g. if you weigh 120g the calculation is 120 X 0.002 = a possible error of 0.24g. The capacity of the DK-1000 is 1000g, so 1000 X 0.002 = a possible error of 2g. There's no point in complaining that at 1000g. the scale is only accurate to the nearest 2g (when weighing 1000g) because this is simply how it's designed. Generally the higher the price the more accurate, irrespective of the resolution.

- Calibration

The reading on a measuring device (any measuring device, e.g. thermometer, weighing machine, clock...anything) must match the units it is measuring (e.g. degrees, grams, minutes). This matching-up is called calibration. Electronic machines go out of calibration, it is the nature of electronics. Most can be recalibrated. In the scientific industry all machines need to be recalibrated regularly (usually once a year), a technician will call to do this, the charge is about £100.00. But nobody is going to pay £100.00 to recalibrate a scale that costs just £20.00.

Nearly all balances include calibration instructions which involve pressing buttons in a complicated sequence and placing a weight on the weighing platform (read the instructions for your balance to see which weight is required). But the weight is never included when you buy the balance. High quality calibration weights cost over £50.00 each, we have some 'basic' weights which cost £2.00 to £5.00 and are quite adequate for the balances we sell. When you first get your balance, weigh a selection of coins (if you don't have any weights), make a note of the readings, every few months check that the balance is correct against coins, if you notice errors, buy a weight and recalibrate it. Hopefully this will only be necessary once every couple of years.

Two warnings. Firstly, Do not try to recalibrate a balance without the weight, you will merely reprogram its electronics and will have to send it back to us to be recalibrated properly. Secondly, the very cheap balances (£10.00 to £15.00) go out of calibration regularly, they are not 'faulty', we will not replace them, if you return one we will recalibrate it (If it's under guarantee there will be no charge, if it is out of guarantee there will be a nominal charge) - this is what you get when you by a very cheap digital balance. But look on the bright side, we will recalibrate it - try getting one repaired or exchanged if you bought it on eBay or from a street market!

BUYING GUIDE

In choosing this selection I have to tread a path between items that seem too cheap (e.g. for those who still think anything under £100.00 must be rubbish...technology has moved on!), and at the same time I must be competitive (e.g. for those who have seen balances in street markets for under £10.00 and think anything over £20.00 is expensive). I hope my selection is both reliable and good value.

MECHANICAL WEIGHING MACHINES

The simplest balance is the 'gravity balance' in the style of the Victorian Letter Balance - which is why I call it a 'postal scale.' You can, of course, weigh anything that will fit to the clip and is under 100g. But do bear in mind that for £2.00 you are not buying a high-precision instrument.

Most the the weighing machines in this section are the very high-precision spring balances by the Swiss company PESOLA, and two of the models are made especially for QUICKTEST, marked in Troy ounces for weighing gold and silver (not the Avoirdupois ounce used for weighing food). Spring balances are neater and more reliable than digital balances, they can be as accurate (see above) as digital balances, they are more convenient for weighing large or bulky objects. Choose from medium and high capacity (600g or 1Kg or 2.5Kg), or very high capacity (5Kg). These high quality spring balances vary in price from £25.00 to £55.00.

We also have some cheap models, prices start at £2.00 (click here then scroll down to the last few items on the page) but please remember, you get what you pay for in reliability (ie giving consistent readings), durability (ie how long it lasts) and accuracy (see above).

DIGITAL BALANCES, REGULAR LINES / SMALL INCLUDING POCKET-SIZE

If you deal in gold and small items of silver; coins and small amounts of scrap; if you need to weigh catalysts, plant and insect samples, powder for ammunition, herbs for making potions - anything small, then you will find it more comfortable to put it on the weighing platform of a small digital balance. Scrap merchants, antiques dealers and market traders like these.

The TANITA are, relatively, expensive but accurate, sturdy and beautifully designed. When people ask me what you get for your money with the TANITA models, I explain that failing a bad accident they should last for years - when you buy one of the cheaper Chinese balances you must be prepared to throw it away if you drop it once, get it slightly wet once, or overload it once. The TANITA models do tend to survive minor accidents and last for years.

DIGITAL BALANCES / TABLE BALANCES

There is a good series of high-capacity good-value no-frills table balances, I call them (imaginatively) TABLE BALANCES, there are three models, all weigh down to 0.1g. and the capacities are: 500g, 1Kg, and 3Kg.

The 5Kg balance (weighs down to 1g) has some good features, the display is backlit and there's a large weighing pan for pouring things (food...coins) and it also has a 'rack' for placing large envelopes and padded bags in an upright position so that you can still see the display. The display is unusual too, it reads in Kg and g, and lb and oz. I shall explain. Most displays show only decimal, e.g. 2361g or 12.187lb, this display will read (in this example) 2Kg. 361g or 12lb 3oz. This is the one I use myself, in the office, for weighing products (because I have to enter the weight of each item on this web site so that the computer can calculate the shipping costs). We do, of course, have a proper grown-up 30Kg parcel scale in the postroom, but it is this 5Kg. balance I use on my desk.

Finally, Trading Standards Approved balance, approved for shop use (in fact, anywhere that goods are bought or sold by weight).