Appendix 6 Terminology
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RECTIFIER For the PW3335, the rectifier refers to the rectification method. (p.42)
AC + DC
Displays true RMS values for DC only, AC only, or mixed DC and AC voltage and current.
True RMS:
The waveform including harmonic components is determined based on the RMS
calculation formula.
AC + DC Umn
Umn: Abbreviation for “voltage mean.”
Displays mean value rectified RMS equivalents for DC only, AC only, or mixed DC and AC
voltage. Current values are displayed as RMS values.
Mean value rectified RMS equivalents:
The input waveform is treated as an undistorted sine wave (single frequency only). The
AC signal mean is calculated, converted to an RMS value, and displayed. The measure-
ment error increases when the waveform is distorted.
FND
FND: Abbreviation for “fundamental.”
Extracts and displays the fundamental wave component only using harmonic measurement.
Ripple rate
The ratio of the AC component contained in a DC voltage or DC current to the DC compo-
nent.
Total harmonic voltage
distortion
Total harmonic current
distortion
(THD)
THD: Abbreviation for “total harmonic distortion.”
There are two types of THD:
THD-F:
The ratio of the size of the total harmonic component to the size of the fundamental wave,
expressed as a percentage using the following equation:
(for the PW3335, calculation of up to the 50th order depending on the input frequency)
This value can be monitored to assess waveform distortion for each item, providing a yard-
stick that indicates the extent to which the total harmonic component is distorting the funda-
mental waveform.
THD-R:
The ratio of the size of the total harmonic component to the size of RMS values, expressed
as a percentage using the following equation:
(for the PW3335, calculation of up to the 50th order depending on the input frequency)
THD-F is typically used. The PW3335 displays THD-F as THD. (THD-R is not available as a
measurement parameter.)
Zero-cross filter
The PW3335 calculates parameters such as RMS values and active power based on one
cycle of the synchronization source’s input waveform (voltage U or current I). This cycle is
obtained by detecting the zero-cross interval (the interval from one rising edge until the next
cycle’s rising edge). A filter used when it is not possible to accurately detect the zero-cross
due to the effects of ringing or noise close to the input waveform’s zero-cross point.
Zero-suppression Functionality for treating values that are less than a certain threshold as zero.
Terminology Description
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