What the Eagle™ Records
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starting current of the air conditioner. The voltage interval will
probably have a dip at the same time.
The most frequent reason to use an interval smaller than one
minute is for large loads that cycle on and off more frequently than
one minute. For example, if an elevator is causing power quality
problems, and it only takes 10 or 20 seconds to start at one floor
and stop at another, a one-second interval is probably necessary;
otherwise, the entire elevator travel will occur during a single
interval. In this case, the Eagle should not be left to record for
days, since it will only hold the last few hours of interval graph
data. The best use in this case is to set the interval graph to one
second, cycle the load (such as the elevator) for a while in an
attempt to reproduce the problem, and then download the data
recorded by the Eagle. In general, the interval should be smaller
than the quickest cycling time of a problem load.
The most frequent reason to use an interval larger than one
minute is to increase the recording time. Setting the interval to
two minutes doubles the recording time, without a serious loss of
time resolution. Other common settings are five and fifteen
minutes, used to match metering or billing increments or
regulatory time periods.
The second interval graph setting is the “Interval Graph Overwrite”
mode or “wrap-around” mode, as we discussed earlier. The best
setting for this depends on how the Eagle will be used. Some
users leave a recorder at a problem site until the customer calls
with a power quality complaint. The recorder is set to a small
interval, such as one minute or thirty seconds, and interval graph
overwrite is enabled. Because interval graph overwrite is enabled,
the interval graphs always have the latest few days of data in
memory, by discarding the old data. The data from the Eagle is
then downloaded, and has the most recent days of interval graph
data in memory, no matter how long it was recording. This recent
data will most likely have the voltage disturbance in it. Other
users will disable interval graph overwrite, and leave a recorder at
a problem site where the power quality problem will definitely
occur soon. The Eagle will record the first few weeks of interval
graph data, and then it will stop interval graph recording. The
Eagle can be downloaded later, knowing that the beginning of the