Accuracy classes are defined and used in
IEC
The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...
and
ANSI
The American National Standards Institute (ANSI ) is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organi ...
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'', while ''precision'' is how close the measurements are to each other ...
from IEC-751 that requires accuracy of ± 0.15 degrees
Celsius
The degree Celsius is the unit of temperature on the Celsius scale (originally known as the centigrade scale outside Sweden), one of two temperature scales used in the International System of Units (SI), the other being the Kelvin scale. The ...
. 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.
Measurement
{{measurement-stub