2. Meter classes

IEC defines for meters a base currentI _b , which is the current value according to which certain meter characteristics are set, and a maximum currentI _max , which is the highest current value at which the meter must meet accuracy requirements.

The class index is the number that gives the permissible limit of the percentage error, for all current values between 0.1 I _b and I _max , for a power factor equal to unity (and, in the case of polyphase meters, with balanced loads), when the meters are tested under reference conditions as defined in the recommendations.

The following meter classes are currently available:

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