Meter classes
Alternating current meters

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:

• classes 0.5; 1 and 2 for electromechanical active energy meters;

• classes 0.2; 0.5; 1 and 2 for electromechanical reactive energy meters;

• classes 2 and 3 for reactive energy meters.

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