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FAQ - Legal for Trade Applications
Frequently Asked Questions:
- What is the difference between Legal for Trade and non-Legal for Trade?
- My jewelry scale is calibrated once a year when it is serviced. But how often do I need to test it in between?
- Why does a Legal for Trade scale cost more than a regular scale?
- Why should I buy a Legal for Trade scale if I don't intend to use it in a business transaction?
- Is an Approved balance or scale better than a regular one?
- What is the different between 'Approved' and 'Legal for Trade'?
- What do e=d and e=10d mean?
- Why does my Legal for Trade scale show the last digit in brackets?
- My scale has d = 0.01 g. Does this mean I can weigh 0.01 g on it?
- Where can I find out if I need a Legal for Trade or a regular scale?
- Can I do an external calibration on my Legal for Trade balance?
1. What is the difference between Legal for Trade and non-Legal for Trade?
Legal for Trade balances and scales must be used when weight forms part of the business transaction. For example, the price of a gold necklace depends directly on the weight of gold it contains. Conversely, when tracking how much of a diamond has been polished away, a Legal for Trade scale is not required. Whilst still very important to the business, this weight measurement is not part of a sales transaction.
2. My jewelry scale is calibrated once a year when it is serviced. But how often do I need to test it in between?
Through normal use, the performance of a scale will change over time. Calibrating a scale once per year by an authorized service technician is always a good idea in order to maintain a documented record of its performance. The amount of testing required in between depends upon the level of accuracy you require. Higher accuracy requires more frequent testing. However, JET scales feature internal test weights and FACT technology which tests and adjusts the scale automatically. When using FACT, the amount of testing can typically be reduced. Please contact us for precise advice on testing a balance and scale.
3. Why does a Legal for Trade scale cost more than a regular scale?
To qualify for Legal for Trade, there are many additional requirements that a scale must fulfill over and above those of a regular scale. For example, the additional software adaptations necessary will require extra investment from the manufacturer, adding to the price of the scale. The extensive testing that every Legal for Trade scale undergoes, as well as the required associated documentation, also contribute to the additional cost.
4. Why should I buy a Legal for Trade scale if I don't intend to use it in a business transaction?
When you buy a Legal for Trade balance or scale, you have the reassurance of knowing that you have a quality scale that has been independently tested to verify its performance.
5. Is an Approved balance or scale better than a regular one?
METTLER TOLEDO balances and scales are all manufactured to the same high quality. However Legal for Trade versions undergo additional independent testing. When comparing an equivalent scale from an alternative manufacturer that does not offer a Legal for Trade version, it may be worth considering why it does not have the certification.
6. What is the different between 'Approved' and 'Legal for Trade'?
Approved and Legal for Trade mean the same.
7. What do e=d and e=10d mean?
d is the smallest division that a balance or scale can display.
e is the smallest interval on a balance or scale that can be used in a business transaction.
For example, a scale has d = 0.001 g, providing weight results to 3 decimal places. In the case that e=d, the scale can be used in business transactions measuring weight to 3 decimal places (0.001 g). In the case that e=10d, the balance can only be used in business transactions measuring weight to 10 x 0.001 g or 0.01 g.
8. Why does my Legal for Trade scale show the last digit in brackets?
When the e value of the scale is greater than the d value (see previous question) the digit(s) in the weight result that cannot be included in a business transaction are shown in brackets.
9. My scale has d = 0.01 g. Does this mean I can weigh 0.01 g on it?
No. Every weight measurement made on a balance or scale has a degree of uncertainty. When the item being weighed is very small, the error due to the uncertainty becomes large compared to the weight of the item. Every balance has a point, below which the uncertainty is so high that the weight results cannot be deemed to be accurate. This point is known as the minimum weight. This is the smallest weight you can weigh on your balance. The minimum weight is determined by the service technician during calibration. When you require a higher degree of accuracy, the minimum weight value must be increased (this reduces the level of uncertainty).
10. Where can I find out if I need a Legal for Trade or a regular scale?
The first place to check if you need a Legal for Trade balance or scale is your local or country's Weights and Measures authority or Trading Standards office. In the US, the NIST Handbook 44 provides guidance.
11. Can I do an external calibration on my Legal for Trade balance?
No. Calibration on a Legal for Trade balance or scale can only be performed by a Weights and Measures inspector. However, you can verify the performance of your scale at regular intervals by testing the balance yourself. If you find your balance is no longer true, you should contact your Weights and Measures office. Following a calibration, the inspector will re-seal your balance. You should never break the Legal for Trade seal on your balance as this will invalidate its Legal for Trade certification.