Minnesota requires that commercial scales and all associated equipment have an NTEP certificate of conformance, and be suitable for the transaction which will be conducted on the scale. To determine suitability, the Minnesota Department of Commerce uses the guidelines in Table 8 of section 2.20 Scales in NIST Handbook 44, 2.2 Theory of Tolerances in Appendix A, and definitions of the same handbook.
Table 8 says that the smallest item weighed on a class II scale with a division size of 0.1 g should weigh at least 5 grams (50 divisions). The smallest item weighed on a class II scale with a division size of 0.01 g should weigh at least 0.2 grams (20 divisions).
In addition, the Theory of Tolerances states that the tolerance allowed on a commercial device should not cause economic injury to either the buyer or the seller. A class II scale with a division size 0.1 g is allowed 1 division (0.1 g) maintenance tolerance for weights between 0 and 500 grams. At the current market prices for gold, that tolerance would allow a monetary error in excess of $3 on every transaction.
Handbook 44 requires that all scales be marked with d (Value of Scale Division) or e (value of Verification scale division) if e is different from d . d is the smallest subdivision or the difference between two consecutively indicated or printed values expressed in terms of mass. e is a value, expressed in units of weight(mass) and specified by the manufacturer of a device, by which the tolerance values and accuracy class applicable to the device are determined.
For these reasons, the Weights & Measures Division requires that scales used for precious metal transactions have an e less than or equal to 0.01 g. If the scale is not marked with e , then d must be less than or equal to 0.01g.
In addition, some vendors sell computer software which connects to the scale and which will convert the scale reading into any unit desired. Even if the software claims to be able to convert the scale reading to 0.01 g divisions, it cannot be more accurate than the scale itself. A conversion to hundredths of a gram would be meaningless if the scale only measures in units of tenths of a gram. A scale which has a division size of 0.01 g could use such software for converting grams to pennyweights (dwt) or other units as long as the software meets the requirements of NIST Handbook 44. W&M investigators will be checking the conversions and the compliance with Handbook 44. For example: 0.01 g = 0.006 dwt, but Handbook 44 requires that all divisions be in units of 1, 2, or 5. The software should convert grams in divisions of 0.01 g to divisions of 0.005 dwt.
Precious metal dealers must also comply with the requirements of Minnesota Statute §325F.