A New Fast Computing RMS-to-DC Conversion

A new approach to ac-to-dc conversion is presented, with applicability both to phase-sensitive rectification and to whole-signal determination. In the former case, it provides insensitivity to effects of signal distortion up to any desired harmonic number, with elimination of effects up to the tenth harmonic a practical possibility. In the whole-signal situation with reasonable amounts of distortion, applying the method reduces effects of harmonics up to the tenth as well. In the whole-signal implementation, the computation yields an excellent approach to true rms, for sinusoidal waves with reasonable amounts of harmonic contamination, and for a wide range of other signals as well, including square and triangular waves. Most significantly, performance capabilities of the new converters include speed and dynamic range as well as accuracy. A converter for 400 Hz and higher settles in 110 ms; for 60 Hz and higher, in 400 ms???both much faster than rms converters using thennal devices. Dynamic range exceeds 60 dB.