PPA5xx/15xx user manual
8-5
8.3 Standby power measurement
In order to minimise standby power, some devices operate
in a ‘dormant’ mode whereby power is only drawn from
the supply when needed. These devices draw very little
current for most of the time and then draw a larger
current for a single cycle to charge a reservoir capacitor.
This pattern is repeated on an irregular basis.
Most of the power consumed by devices in this mode is
taken in the periodic higher current cycles so to accurately
measure the power drawn by these devices, so the
instrument synchronises to the power frequency for the
analysis but extends the measurement window to the
irregular period of higher energy pulses. Because the
instrument samples in true real time without any gaps, no
data is missed, and every power cycle is captured.
It is important that ranging is set to manual or up only
autoranging so that the power cycles are not missed while
ranging.