The manufacturer shall specify both the reference accuracy class Ref(x) and the operational accuracy class(es) X(x).

An instrument type is designated a reference accuracy class, Ref(x), corresponding to the best possible accuracy for instruments of the type. After installation, individual instruments are designated for one or more operational accuracy classes, X(x), having taken account of the specific products to be weighed. The class designation factor (x) shall be ≤ 2, and in the form 1 × 10^k, 2 × 10^k or 5 × 10^k where k is a negative whole number or zero.

The reference accuracy class, Ref(x) is applicable for static loads.

For the operational accuracy class X(x), X is a regime relating accuracy to load weight and (x) is a multiplier for the limits of error specified for class X(1) in point 2.2.