What is the benefit of making voltage measurements with a true-RMS calculating meter?
The correct answer is D: RMS is measured for both sinusoidal and non-sinusoidal signals. The benefit of making voltage measurements with a true-RMS calculating meter is that RMS is measured for both sinusoidal and non-sinusoidal signals. True-RMS meters accurately measure the RMS value regardless of waveform shape.
Ordinary AC voltmeters are calibrated for sine waves and give incorrect readings for non-sinusoidal waveforms (like square waves, triangle waves, or distorted signals). True-RMS meters actually calculate the root-mean-square value of the waveform, so they give accurate readings for any waveform shape. This is important when measuring complex signals, distorted waveforms, or signals with harmonics. True-RMS meters are essential for accurate measurements of non-sinusoidal signals common in digital circuits and power electronics.
Exam Tip
True-RMS benefit = Accurate for all waveforms. Remember: True-RMS meters accurately measure RMS for both sinusoidal and non-sinusoidal signals, unlike ordinary meters that only work correctly for sine waves.
Memory Aid
"**T**rue-**R**MS = **T**rue for **A**ll **W**aveforms (think 'TR = TAW')"
Real-World Application
You're measuring the voltage of a square wave signal. An ordinary AC voltmeter (calibrated for sine waves) gives an incorrect reading. A true-RMS meter actually calculates the RMS value of the square wave, giving you the correct measurement. This is essential when working with digital signals, PWM waveforms, or any non-sinusoidal signals.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Inverse Fourier transform is a mathematical operation, not a benefit of true-RMS meters. RMS meters measure RMS directly, they don't perform Fourier transforms.
Option B: Incorrect. True-RMS meters measure RMS voltage, not specifically RMS noise factor. They measure the RMS of whatever signal is present.
Option C: Incorrect. RMS values can be converted to phasor form, but this isn't the specific benefit of true-RMS meters. The benefit is accurate RMS measurement for any waveform.
题目解析
The correct answer is D: RMS is measured for both sinusoidal and non-sinusoidal signals. The benefit of making voltage measurements with a true-RMS calculating meter is that RMS is measured for both sinusoidal and non-sinusoidal signals. True-RMS meters accurately measure the RMS value regardless of waveform shape. Ordinary AC voltmeters are calibrated for sine waves and give incorrect readings for non-sinusoidal waveforms (like square waves, triangle waves, or distorted signals). True-RMS meters actually calculate the root-mean-square value of the waveform, so they give accurate readings for any waveform shape. This is important when measuring complex signals, distorted waveforms, or signals with harmonics. True-RMS meters are essential for accurate measurements of non-sinusoidal signals common in digital circuits and power electronics.
考试技巧
True-RMS benefit = Accurate for all waveforms. Remember: True-RMS meters accurately measure RMS for both sinusoidal and non-sinusoidal signals, unlike ordinary meters that only work correctly for sine waves.
记忆口诀
**T**rue-**R**MS = **T**rue for **A**ll **W**aveforms (think 'TR = TAW')
实际应用示例
You're measuring the voltage of a square wave signal. An ordinary AC voltmeter (calibrated for sine waves) gives an incorrect reading. A true-RMS meter actually calculates the RMS value of the square wave, giving you the correct measurement. This is essential when working with digital signals, PWM waveforms, or any non-sinusoidal signals.
错误选项分析
Option A: Incorrect. Inverse Fourier transform is a mathematical operation, not a benefit of true-RMS meters. RMS meters measure RMS directly, they don't perform Fourier transforms. Option B: Incorrect. True-RMS meters measure RMS voltage, not specifically RMS noise factor. They measure the RMS of whatever signal is present. Option C: Incorrect. RMS values can be converted to phasor form, but this isn't the specific benefit of true-RMS meters. The benefit is accurate RMS measurement for any waveform.
知识点
True-RMS meter, RMS measurement, Sinusoidal signals, Non-sinusoidal signals
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.