Rules for Improving DC and RMS Measurements

Use the following guidelines when determining a strategy for improving DC and RMS measurements:

RMS Levels of Specific Tones

You always can improve the accuracy of an RMS measurement by choosing a specific measurement time to contain an integer number of cycles of sine tones or by using a window function. The measurement of the RMS value is based only on the time domain knowledge of the signal. You can use advanced techniques when you are interested in a specific frequency or narrow frequency range.

You can use bandpass or bandstop filtering before RMS computations to measure the RMS power in a specific band of frequencies. You also can use the Fast Fourier Transform (FFT) to pick out specific frequencies for RMS processing.

The RMS level of a specific sine tone that is part of a complex or noisy signal can be extracted very accurately using frequency domain processing, leveraging the power of the FFT, and using the benefits of windowing.