Datasheet

Test equipment and measurement of efficiency and light load performance AN4165
34/37 Doc ID 023661 Rev 1
As noted in IEC 62301, instantaneous measurements are appropriate when power readings
are stable. The UUT is operated at 100% of nameplate output current output for at least 30
minutes (warm-up period) immediately prior to conducting efficiency measurements.
After this warm-up period, the AC input power is monitored for a period of 5 minutes to
assess the stability of the UUT. If the power level does not drift by more than 5% from the
maximum value observed, the UUT can be considered stable and the measurements can
be recorded at the end of the 5-minute period. If AC input power is not stable over a 5-
minute period, the average power or accumulated energy is measured over time for both AC
input and DC output.
Some wattmeter models allow integration of the measured input power in a time range and
then measure the energy absorbed by the UUT during the integration time. The average
input power is calculated dividing by the integration time itself.