Power factor is measured using Keysight’s Continuous Whole-Cycle Analysis (CWA) which is a gapless measurement technique that always performs measurements on a positive integer number of cycles.
When analyzing power quality there is a Meas Window softkey available. Pressing this softkey will allow you to select a measurement window of 50 ms, 100 ms, 200 ms, 500 ms, 1 s, 2 s, 5 s, 10 s or 20 s. The signal content that is measured depends on the mode you’re in (AC, DC or AC+DC).
The actual window will be slightly longer than the selected value so that the instrument always measures the same number of cycles per window at typical power frequencies (50, 60, and 400 Hz). For example, if you have a 50 Hz signal that is sometimes 49.99 Hz and sometimes 50.01 Hz, a 200 ms window would fit 10 whole cycles of the 49.99 Hz signal, but only 9 whole cycles of the 50.01 Hz signal. So, the 200 ms window is extended in order to ensure 10 whole cycles of frequencies slightly lower than 50 Hz.
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