Division (b) Test equipment

The goal of the test procedures is to accurately measure the TRUE power consumption^f1 of the product. This necessitates the use of a True RMS power or energy meter. There are many such meters available, and manufacturers need to exercise care in selecting an appropriate model. The following factors must be considered when selecting a meter and conducting the test.

Frequency response: Electronic equipment that contains switching power supplies introduces harmonics (odd harmonics typically up to the 21st). If these harmonics are not accounted for in power measurement, the result will be inaccurate. EPA recommends that manufacturers use meters that have a frequency response of at least 3 kHz; this will account for harmonics up to the 50th, and is recommended by IEC 555.

Resolution: For direct power measurements, the resolution of metering equipment must be consistent with the following requirements of IEC 62301:

‘The power measurement instrument shall have a resolution of:

• 0,01 W or better for power measurements of 10 W or less,

• 0,1 W or better for power measurements of greater than 10 W up to 100 W,

• 1 W or better for power measurements of greater than 100 W.^f2 ’

In addition, the measurement instrument must have a resolution of 10 W or better for power measurements greater than 1,5 kW. Measurements of accumulated energy should have resolutions which are generally consistent with these values when converted to average power. For accumulated energy measurements, the figure of merit for determining the required accuracy is the maximum power value during the measurement period, not the average, since it is the maximum that determines the metering equipment and set-up.