Form factor (electronics): Difference between revisions

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Digital AC measuring instruments are often built with specific waveforms in mind. For example, many digital AC multimeters are specifically scaled to display the RMS value of a sine wave. Since the RMS calculation can be difficult to achieve digitally, the absolute average is calculated instead and the result multiplied by the form factor of a sinusoid. This method will give less accurate readings for waveforms other than a sinewave.<ref>{{cite web|last=Tanuwijaya|first=Franky|title=True RMS vs AC Average Rectified Multimeter Readings when a Phase Cutting Speed Control is Used|url=http://www.escoglobal.com/resources/pdf/white-papers/True_G2.pdf|publisher=Esco Micro Pte Ltd|accessdate=2012-12-13}}</ref>

== Properties ==

As discussed above, the form factor is the quotient of the RMS and the ARV. The independent properties and similarities of these two values define the properties of the form factor.

For example, both RMS and ARV are directly proportional to the [[Amplitude]] <math>a</math>. However, their division removes the amplitude from the equation, meaning that form factor of a given waveform is the same regardless of how large or small the alternating current or voltage may be.

The squaring in RMS and the absolute value in ARV mean that both the values and the form factor are independent of the wave function's sign (and thus, the electrical signal's direction) at any point. For this reason, the form factor is the same for a direction-changing wave with a regular average of 0 and its fully rectified version.