User Manual – Rev BE AMETEK Programmable Power
MX Series 169
4.5.3 Accuracy Considerations
Any measurement system has a finite accuracy specification. Measurement
specifications are listed in Section 2. When using the AC source for
measurement purposes, always consider these specifications when interpreting
results. Measurement inaccuracies become more pronounced as the signal being
measured is at the low end of the measurement range. This is particularly
relevant for low current measurements. The MX Series is a high-power AC and
DC source optimized for providing and measuring high load currents. When
powering low power loads, measurement inaccuracies on rms and peak current
measurements will greatly affect derived measurements such as power, power
factor and crest factor.
The measurement system on the MX Series I utilize a data acquisition system
with a 6.6 kHz bandwidth in three-phase mode. The MX Series uses 16 kHz.
This means that high frequency components of the measured signal are filtered
out. Any contribution to the rms value of voltage and current above this cutoff
frequency will not be reflected in the MX Series measurements. When using an
external measurement reference, this may account for discrepancies in
readings.
4.6 Advanced Measurements [3Pi Controller only]
The 3Pi controller offers advanced power analyzer measurement capabilities.
These functions may be accessed from the MEAS button or the MENU 2 screen.
The phase for which the analysis or waveform acquisition is done may be
selected using the PHASE key in three phase configurations. This chapter covers
the use and application of these advanced measurement functions.
4.6.1 Harmonic Analysis
The 3Pi controller’s power analyzer performs fast Fourier transformation (FFT)
on both voltage and current on each available phase. The resulting frequency
spectrum can be displayed on the LCD display in a tabular as well as a graphical
mode.
4.6.1.1 Acquiring FFT data
To perform an FFT analysis on the output of the AC source, proceed as follows:
1) Press the MEAS button four times or until the
HARMONICS/TRACE ANALYSIS screen appears.
2) Move the cursor to the FUNCTION field and select VOLT or
CURR. (The BOTH selection will default to CURR as only one
FFT result can be displayed at a time.)
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