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Question 451

What is the benefit of making voltage measurements with a true-RMS calculating meter?

  1. An inverse Fourier transform can be used
  2. The signal’s RMS noise factor is also calculated
  3. The calculated RMS value can be converted directly into phasor form
  4. RMS is measured for both sinusoidal and non-sinusoidal signalsCorrect answer

Explanation

A true-RMS meter computes the square root of the mean of the squared instantaneous values, so it reports the correct heating-equivalent value whatever the waveform shape. Simpler average-responding meters are scaled by a fixed form factor that is valid only for a pure sine wave and read incorrectly on distorted, pulsed or noise-like signals.

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Question 451: What is the benefit of making voltage measurements with a… · FCC Amateur Extra Class (Element 4) · Questena