AEMC’s Power and Energy Loggers Model PEL instruments provide all the necessary functions
and features for power and energy data logging for most 50Hz, 60Hz, 400Hz, and DC distribution
systems worldwide.
Primary users include contractors performing power system evaluation and monitoring.
These instruments measure phase-to-phase, phase-to-neutral, and neutral-to-earth voltage,
measuring up to 1000 volts.
They also measure phase and neutral current, using a variety of external current sensors.
Measurement data is then used to calculate numerous values, including active, reactive,
and apparent power and energy; crest factor, harmonics and total harmonic distortion; and
others.
The AEMC PowerPad family of instruments combine data logging with sophisticated power quality
analysis.
These instruments are portable three-phase network analyzers designed to:
Measure RMS values, powers, and fluctuations of electric hookups
Deliver a snapshot of the principal characteristics of a three-phase network
And track variations of specified parameters over time.
These instruments enable utility company technicians and engineers to measure single and three-phase
networks, and perform diagnostics and power quality analysis.
Trend data can be recorded for days, weeks or even months.
Inrush current can also be captured and stored.
When recording data, AEMC PowerPad and PEL instruments perform measurement aggregation.
This involves calculating the average value for a measured parameter over a user-specified
time interval.
Aggregation saves storage space by reducing the number of measurements recorded over the
duration of the recording.
It also ensures accurate data by including all individual measurements in the aggregation,
rather than periodically taking single measurements.
The interval over which aggregation is performed can be selected by the user.
Some AEMC models allow you to do this through the instrument interface, while others require
configuration via AEMC’s DataView software.
Depending on instrument model, aggregation can be as short as one second or as long as
one hour.
Shorter periods are recommended for short recordings containing minute-by-minute detailed
measurements, while longer periods are ideal for monitoring long-term trends for several
weeks or months.
The typical aggregation period used by utility companies in the U.S. is 15 minutes, while
in Europe the period is typically 10 minutes.
Note that aggregation does not affect how often an instrument takes a measurement.
During the recording session the instrument takes measurements at a constant rate, such
as 128 samples per cycle for the PEL.
At the end of each aggregation period, the instrument automatically applies a mathematical
formula to determine the average of all the measurements taken.
Depending on the instrument and measured parameter, the average is determined by calculating the
root mean square, arithmetic mean, or other calculation.
This average is then recorded in the instrument memory.
The time at which the aggregated measurement is recorded in memory depends on the instrument
model.
On PowerPad instruments, the time stamp of the aggregated measurement for most parameters
is the beginning of the aggregation period, while on PEL instruments the time stamp is
the end of the period.
For example, if you schedule a recording on the PEL to begin at 12:00 and end at 1:00,
and select a 15 minute aggregation period, the recording will consist of 4 measurements
(12:15, 12:30, and so on until the final measurement at 1:00).
On a PowerPad with the same configuration, most aggregated measurements will be time
stamped at 12:00, 12:15, and so on, with the final measurement at 12:45.
The one exception are energy measurements, which in PowerPad recordings are time stamped
at the end of the aggregation period, similar to PEL instrument.
Note that aggregation will only begin or end at clock times evenly divisible by the aggregation
period.
For instance, if a one-hour recording on the PEL begins at 12:06 with a 15 minute aggregation
period, the first aggregation begins at 12:15 and ends at 12:30.
Aggregation is then performed every 15 minutes, with the final aggregation ending at 1:00.
Although the recording continues until 1:06, no aggregation will be performed for the final
6 minutes.
Therefore for this recording, only 3 aggregated measurements will be made.
For more information about AEMC PowerPad and PEL instruments, please visit our web site.
And be sure to visit our YouTube channel for additional instructional videos on other topics
in electronics.