Appendix 6 Terminology
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Appendix 6 Terminology
Terminology Description
Crest factor
Crest factor, which is the ratio of the crest value (peak value) to the RMS value of the volt-
age waveform or current waveform, and can be defined with the following expression.
Crest factor = crest value (peak value)/RMS value
For a pure sine wave, the crest factor is 1.4142… ( ). For pure DC current, it is 1.
For measuring instruments such as power meters, the crest factor may also indicate the
magnitude of the internal circuitry’s dynamic range.
Effect of power factor
Error caused by the phase difference between voltage and current in the instrument’s inter-
nal circuitry. The effect of power factor affects active power measured values.
Harmonics
HRM
A phenomenon caused by distortions in the voltage and current waveforms that affect many
devices with power supplies using semiconductor control devices. In the analysis of non-
sine waves, the term refers to one RMS value among the components with harmonic fre-
quencies.
IEC61010
The International Electrotechnical Commission (IEC) has established IEC 61010 as a safety
standard for measuring instruments. To ensure that measuring instruments can be used
safely, this standard defines safety levels as a series of measurement categories (CAT II to
CAT IV) based on the locations in which instruments are used. (p.4)
Instrument loss
Instrument loss, which is caused by the input resistance of power measuring instruments’
voltage and current inputs, increases with the input voltage and input current as well as with
certain connection methods, and this in turn causes the error component of measured val-
ues to increase.
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