Gold scales and jewellery scales

What a gold scale is

No manufacturer puts "gold scale" on the box. It is a precision balance that can do three things: read to 0.01 g or finer, switch to carats (ct) and usually also to troy ounces (ozt) and pennyweights (dwt), and stand steady enough to make that last digit count. Every scale on this page has carats as a weighing unit; that is how they were selected. Here you will find compact jewellery scales for the counter, analytical balances with draught shield for loose stones, and pocket scales for a valuation away from the shop.

Carat means two things

The word causes confusion, including among customers at the counter. The carat as a weight (ct) is the unit for gemstones and pearls: one carat is 0.2 gram. That is the unit the scale displays. The carat as a fineness (kt) tells you how much gold is in an alloy: 24 carat is pure gold, 18 carat is 750 parts per thousand, 14 carat is 585. You do not weigh the fineness; you read it from the hallmark or determine it with a test. The scale gives the weight; the value follows from weight times fineness times the day's price.

Buying and selling by weight: verified

As soon as the price follows from the weight, when buying gold, selling bars and coins or a stone priced per carat, a verified scale is a legal requirement. For precious metals and gemstones, that is a scale of accuracy class II or I; Class III, the ordinary trade class of the retail scale, is too coarse for this. You can recognise the verified scale by the green M mark on the data plate; what else it shows is explained under what is a verified scale and OIML classes explained. With a verified precision balance, pay attention to the verification scale interval e: it is often ten times coarser than the readability d, and for legal purposes only e counts. Choose the verified version of the model and it arrives verified from the factory; all verifiable models are also listed under verified scales.

Which readability you need

For gold and silver by the gram, 0.01 g is the usual step: fine enough for a ring or a necklace, and the scale stays quick and insensitive. For loose gemstones you work in hundredths of a carat, and then you need 0.001 g; that is 0.005 ct. Anyone making up alloys or weighing samples for an assay ends up with an analytical balance of 0.0001 g. Do not choose a capacity larger than you need: the larger the capacity at the same readability, the more sensitive the scale is to draughts and vibration. If in doubt, read which scale do I need or give us a call.

On the counter: draughts, vibration and levelling

A scale that reads to a milligram also weighs the air flow from a door opening. Place it on a firm surface, away from the door, the air conditioning and the till drawer, and level it using the adjustable feet and the spirit level. From 0.001 g, a draught shield is not a luxury; most models in that class have one as standard. Let the scale warm up after switching it on before you weigh, and let the customer watch: a display on the back or a second display shows what you see.

Real gold? Density tells you a lot

Gold is heavy for its volume, and that is something you can weigh. With a density kit you first weigh the object in air and then submerged in water; the scale calculates the density. A result far from the expected value for the fineness is a reason to look further. It is not an assay and it does not work on hollow or stone-set pieces, but as a first check when buying it is quick and leaves the object intact. For KERN precision and analytical balances we supply the matching density determination kit; ask about it with the model of your choice.

Checking, calibration and re-verification

You check a gold scale yourself with a check weight of the right class: a weight close to the point where you weigh most, on the scale once a day or once a week, and the result in a logbook. If it deviates, you adjust it, at the push of a button on models with internal adjustment. For your quality system or your insurer we calibrate with a certificate. If the seal of a verified scale has been broken or it has been repaired, re-verification is arranged through the manufacturer, including for a scale you did not buy from us.