2–16 EPM 6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE
CHAPTER 2: ELECTRICAL BACKGROUND
accuracy; at frequencies above about 1200 Hz they pass almost no information. So when
instrument transformers are used, they effectively filter out higher frequency harmonic
distortion making it impossible to see.
However, when monitors can be connected directly to the measured circuit (such as direct
connection to 480 V bus) the user may often see higher order harmonic distortion. An
important rule in any harmonics study is to evaluate the type of equipment and
connections before drawing a conclusion. Not being able to see harmonic distortion is not
the same as not having harmonic distortion.
2.5.4 Waveform Capture
It is common in advanced meters to perform a function commonly referred to as
waveform capture. Waveform capture is the ability of a meter to capture a present picture
of the voltage or current waveform for viewing and harmonic analysis. Typically a
waveform capture will be one or two cycles in duration and can be viewed as the actual
waveform, as a spectral view of the harmonic content, or a tabular view showing the
magnitude and phase shift of each harmonic value. Data collected with waveform capture
is typically not saved to memory. Waveform capture is a real-time data collection event.
Waveform capture should not be confused with waveform recording that is used to record
multiple cycles of all voltage and current waveforms in response to a transient condition.
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