Accuracy classes are defined and used in

IEC The International Electrotechnical Commission (IEC; ) is an international standards organization that prepares and publishes international standards for all electrical, electronic and related technologies. IEC standards cover a vast range of ...

and

ANSI The American National Standards Institute (ANSI ) is a private nonprofit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organiz ...

standards. Classes are denoted by either a letter or percentage. For example, Class B is a temperature

accuracy Accuracy and precision are two measures of ''observational error''. ''Accuracy'' is how close a given set of measurements (observations or readings) are to their ''true value''. ''Precision'' is how close the measurements are to each other. The ...

from IEC-751 that requires accuracy of ± 0.15 degrees

Celsius The degree Celsius is the unit of temperature on the Celsius temperature scale "Celsius temperature scale, also called centigrade temperature scale, scale based on 0 ° for the melting point of water and 100 ° for the boiling point ...

. Class 0.5 is an ANSI C12.20 accuracy class for electric meters with absolute accuracy better than ± 0.5% of the nominal full scale reading. Typically, a class specifies accuracy at a number of points, with the absolute accuracy at lower values being better than the nominal "percentage of full scale" accuracy. Accuracy classes such as IEC's 0.15s are a 'special' high accuracy class. Calculation for accuracy of class 1 meter: 1600 impulse/KWh and considering, P.F= 1 and LOAD = 100w Revolution time, Rt = (3600×Kh×1)/Load(w) ''Kh = 1000/(impulse/Kwh=1600) Rt = (3600×0.625×1)/100 Rt = 22.5sec tandard %of error = (Ft-Rt)/Rt The positive or negative result indicates whether the meter is fast or slow. If the result is positive, then the meter is fast, while negative means the meter is slow.

References

Measurement {{measurement-stub