To calibrate a gold scale, level it, close the draft cover, let it settle at zero, then run its calibration mode with the certified test weight named in its manual. Use a weight of class F2 or better, the class OIML R 111 names for weighing precious metals and stones. A 200 g F2 weight may be off by no more than 3 mg, and the scale should be checked with a second weight afterwards.
On Omace digital scales, calibration mode opens when you press and hold the TARE key for about 5 seconds. The calibration weight the display then asks for differs by model, so read it from the display or the manual before you start.
Why a gold scale needs class II accuracy
Gold is sold by weight, so every 10 mg on the scale shows up on the bill. The Ace JS-6002 gold weighing scale reads up to 600 g in 0.01 g (10 mg) steps, with a clear cover that keeps moving air off the pan.
State rules set the accuracy class for this trade. Delhi's Legal Metrology (Enforcement) Rules, 2011, for example, allow only class II or class I weighing instruments, or class A or B beam scales, for gold, silver, ornaments and precious stones. The same rules require bullion weights for precious metals and carat weights for precious stones.
Other states publish their own enforcement rules, so confirm the class with your state's Legal Metrology office before buying a scale for the counter.
OIML accuracy classes and the d and e numbers
OIML R 76 sorts weighing scales into four accuracy classes by their verification scale interval, e, and the number of intervals, n = Max ÷ e:
| Class | Name | Verification interval e | Number of intervals n | Minimum capacity |
|---|---|---|---|---|
| I | Special | 0.001 g or more | 50,000 or more | 100 e |
| II | High | 0.001 g to 0.05 g | 100 to 100,000 | 20 e |
| II | High | 0.1 g or more | 5,000 to 100,000 | 50 e |
| III | Medium | 0.1 g to 2 g | 100 to 10,000 | 20 e |
| III | Medium | 5 g or more | 500 to 10,000 | 20 e |
| IIII | Ordinary | 5 g or more | 100 to 1,000 | 10 e |
The display step, d, and the verification interval, e, are not always the same. R 76 lets class I and II scales use an e up to ten times d, so a scale that displays 0.01 g may be verified at e = 0.1 g. A class II nameplate shows the class, Max, Min and e, and also d when d is smaller than e.
R 76 also notes that testing a scale to an e below 1 mg is not normally feasible, because of the uncertainty of the test loads. That matters for 0.001 g balances.
How much error a 600 g gold scale may show
R 76 sets the maximum permissible error in multiples of e and doubles it once the scale is in service. For a 600 g scale, the allowance depends on the e on its nameplate:
| Load | e on the nameplate | At first verification | In service |
|---|---|---|---|
| Up to 50 g | 0.01 g | ±0.005 g | ±0.01 g |
| 50 g to 200 g | 0.01 g | ±0.01 g | ±0.02 g |
| 200 g to 600 g | 0.01 g | ±0.015 g | ±0.03 g |
| Up to 500 g | 0.1 g | ±0.05 g | ±0.1 g |
Two scales with the same 0.01 g display can carry very different allowances. Read the nameplate before you judge a reading or compare two scales.
Choosing the right test weight
OIML R 111 sets how far each class of weight may be from its nominal value. R 76 then limits a test weight's error to one third of the scale's permitted error at that load.
| Weight class | 200 g may be off by | 500 g may be off by | Intended use in R 111 |
|---|---|---|---|
| E2 | ±0.3 mg | ±0.8 mg | Class I scales |
| F1 | ±1.0 mg | ±2.5 mg | Class I and II scales |
| F2 | ±3.0 mg | ±8.0 mg | Precious metals and stones on class II scales |
| M1 | ±10 mg | ±25 mg | Class III scales |
On a 600 g scale with e = 0.01 g, the first-verification limit at 200 g is ±0.01 g, so the test weight may be off by 3.3 mg at most. A 200 g F2 weight (±3 mg) just passes and an F1 weight passes easily, while an M1 weight (±10 mg) does not. If the nameplate shows e = 0.1 g, the limit at 200 g is ±0.05 g, and an M1 weight is good enough.
R 111 also says weights should be handled and stored so they stay clean. Lift them with tweezers or gloves and keep them in their case.
Some Omace balances come with their weight: the Ace JS-3003 precision weighing balance, which reads 300 g in 0.001 g steps, includes a 200 g calibration weight.
Calibration steps for a 0.01 g gold scale
- Place it well. Use a firm, level table away from fans, AC vents and open windows.
- Level it. If the scale has a level indicator, turn the feet until the bubble sits in the centre circle.
- Close the cover. Shut the cover or glass doors so moving air cannot push the last digit around.
- Restart it. Switch the scale fully off and back on before you calibrate, then let the display settle at 0.
- Clean the pan. Remove dust and press TARE so the empty pan reads 0.
- Run the calibration mode. On an Omace scale, press and hold TARE for about 5 seconds. Place the weight the display asks for in the centre with tweezers, close the cover and wait for the scale to confirm.
- Check zero. Remove the weight; the display must return to 0.
- Check with a second weight. Weigh a different certified weight, such as 100 g, and compare the reading with the error table.
- Check the corners. Place one third of the capacity, 200 g on a 600 g scale, on each quarter of the pan in turn.
- Check repeatability. Weigh the same load three times; the readings must agree within the permitted error.
The Ace KS-600 digital jewellery scale and the JS-6002 both list manual calibration in their specifications. Omace's manuals also note that moving a scale to a new table can change the reading, so recheck it with a known weight after every move.
On a stamped trade scale, do not open the calibration. A stamped scale is sealed, and only a registered repairer may recalibrate it. OIML R 76 requires the calibration adjustment of class II scales to be sealed, and a broken seal means the scale must be verified again.
Grams, carats, tola and troy ounces
NIST gives the exact conversions jewellers use. One metric carat is exactly 0.2 g, one troy ounce is 31.10348 g and one pennyweight is 1.555174 g. An ordinary avoirdupois ounce is 28.34952 g, lighter than a troy ounce.
Bills in India must still be in standard units. Section 4 of the Legal Metrology Act, 2009 bases every unit of weight on the metric system, and Section 11 bars quoting a price or issuing an invoice in anything other than a standard unit.
The Ace JS-6002 shows grams, carats and tola, and the Ace KS-600 adds ounces, grains, pennyweight and troy ounces. One tola is 11.6638 g, or 180 grains. Use tola only as a reference beside the gram figure.
Carat weight versus karat purity
A carat, written with a C, is a weight of 0.2 g used for gemstones. Gold purity is a different measure, written with a K, and no scale can show it.
The Bureau of Indian Standards hallmarks gold jewellery in six purity grades under IS 1417: 14K (585), 18K (750), 20K (833), 22K (916), 23K (958) and 24KS (995). The figure in brackets is the fineness in parts per thousand.
A BIS hallmark has three marks: the BIS logo, the purity grade and a six-digit alphanumeric HUID. Buyers can check the HUID with the Verify HUID feature in the BIS Care app. Weight comes from the scale; purity comes from the hallmark.
Legal Metrology verification for jewellery counters
Section 24 of the Legal Metrology Act, 2009 requires a scale used in any sale to be verified before use. Section 33 fines the use of an unverified scale ₹2,000 to ₹10,000, and a repeat offence can bring up to one year in prison as well.
An electronic gold scale is re-verified every 12 months. Rule 27 of the Legal Metrology (General) Rules, 2011 gives the 24-month cycle only to weights, beam scales and counter machines, and bars a repaired scale from use until it is re-verified and stamped. After the Jan Vishwas (Amendment of Provisions) Act, 2026, repairers need a registration certificate under Section 23 of the Act.
For choosing a scale, see the jewellery scale buying guide; for small scales, see how to calibrate a pocket scale; and for the general method, see how to calibrate a digital weighing scale.
Omace gold and jewellery scales
- The Ace JS-6002 gold weighing scale reads 600 g in 0.01 g steps on green LED displays at the front and back, for ₹9,999 (October 2026).
- The Ace KS-600 digital jewellery scale reads 600 g in 0.01 g steps in seven units and runs on AAA batteries or an adapter, for ₹2,999.
- The Ace JS-5003 electronic balance reads 500 g in 0.001 g steps inside a glass windshield, with a level indicator, for ₹27,999.
- The Ace JS-3003 precision weighing balance reads 300 g in 0.001 g steps and includes a 200 g calibration weight, for ₹22,499.
The full range is in jewellery weighing scales. Jewellery brands that want scales under their own name can use Omace's private label service.
Omace Brands Private Limited has made and supplied weighing scales in India since 1994 from Bagru, Jaipur. Every Omace scale is checked before dispatch, and store purchases carry a 2-year warranty on manufacturing defects. More about Omace. Omace scales are made in India. As a manufacturer, Omace Brands Private Limited holds ISO 9001:2015, ISO 13485:2016 and EU MDR quality certificates, and CE and US FDA compliance certificates; each is listed with its certificate number on the Omace certificates page.
