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When is the error under testing of energy meter directly obtained?
The meter under test and the rotating substandard meter constants are 1.
The meter under test and the rotating substandard meter constants are different.
The meter under test and the rotating substandard meter constants are same.
The meter under test and the rotating substandard meter constants are zero.
The meter under test and the rotating substandard meter constants are same.
The error under testing of an energy meter is directly obtained when the meter under test and the rotating substandard meter possess identical meter constants. This synchronization allows for a direct comparison of the number of revolutions within a specific interval, simplifying the percentage error calculation.
IS 13779:1999
The error under testing of an energy meter is directly obtained when the meter under test and the rotating substandard meter possess identical meter constants. This synchronization allows for a direct comparison of the number of revolutions within a specific interval, simplifying the percentage error calculation.
Percentage┬аError=NsтАЛNtтАЛтИТNsтАЛтАЛ├Ч100%, where NtтАЛ is the number of revolutions of the meter under test and NsтАЛ is the number of revolutions of the standard meter.
Meter┬аConstant┬аK=Energy┬аin┬аkWhRevolutionsтАЛ
During calibration, the energy meter under test and a substandard reference meter are connected in series to the same load. The percentage error is determined by comparing the revolutions of both. If the meter constants KtтАЛ (revolutions per kWh for test meter) and KsтАЛ (revolutions per kWh for standard meter) are identical, the error becomes a direct function of the difference in revolutions, eliminating the need for complex scaling factors.
Identical meter constants simplify the comparison process significantly.
The test is performed by comparing the speeds of the two rotating discs.
If KtтАЛ=KsтАЛ, the ratio of energy measured is directly proportional to the ratio of their revolutions.
This method minimizes human error in reading and calculation.
Simplified calculation of percentage error.
Reduces potential for arithmetic errors during field testing.
Increased speed of calibration.
Requires availability of a substandard meter with a specific constant matching the test meter.
Inflexible if the test meter has a non-standard constant.
Field calibration of induction-type energy meters.
Laboratory testing and benchmarking of electromechanical meters.
Option B is incorrect because if the constants differ, a correction factor involving the ratio KtтАЛ/KsтАЛ must be applied, complicating the direct evaluation.
In modern digital meters, calibration is often done via software pulse counting rather than mechanical disc revolution comparison.
C is correct тАФ The error under testing of energy meter is directly obtained when the meter under test and the rotating substandard meter constants are same.
Always remember that in calibration, the term 'meter constant' relates the number of revolutions of the disc to the total energy consumed; equating these constants simplifies your error equations.
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