What the Eagle™ Records
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The current, power, and power factor histograms are useful for
distribution minute histograms line or load profiling. For these
histograms, the few cycles at the extremes are usually
unimportant: the vast majority in the middle is the good data.
Minute Histograms
The minute histogram provides a much “smoother” version of the
cycle histogram. Quick sags and swells are averaged out of the
data, to show the nominal voltage or current level every minute.
Voltage regulation problems are easy to see in the minute
histogram.
What is Recorded
The minute histogram is similar to the cycle histogram. During
each minute of the recording session, the voltage is averaged
(every cycle is included). At the end of the minute, the histogram
bin counter for that average value is incremented. The result is a
histogram of one-minute average voltages, instead of one-cycle
voltages. For example, if the voltage were 123V for 55 seconds,
then 115V for 5 seconds, the average would be 122V, and the
122V bin counter would be incremented. If the interval graph
interval is also set to one minute, then the interval graph voltage
averages will match the minute histogram counts.
Like the cycle histograms, there are no settings for the minute
histogram. All available minute histograms in an Eagle are always
recorded, regardless of the settings for any other record types.
Memory does not run out for a minute histogram; it just keeps
classifying measurements into the bins (by incrementing the bin
counters) as long as the recording session lasts. All Eagle
recorders will record voltage and current minute histograms.
Suggested Uses
The voltage minute histogram can reveal voltage regulation
problems. Ideally, the line voltage should be at the same value
every minute. The larger the spread in the minute histogram, the
more the voltage is varying. The center of the spread is
(hopefully) the target regulation voltage. This information is also
present to an extent in the voltage interval graph, depending on