https://www.analog.com/cn/resources/design-notes/autoranging-true-rms-converter.html
Design Note 339: An Autoranging True RMS Converter | ADI 公司
The LTC1966 is a true RMS-to-DC converter that uses a ∆Σ computational technique to make it dramatically simpler to use, sign
true rms converterdesignnoteautorangingadi