This chip from Analog Devices computes a precise dc equivalent of the rms value ac waveforms, including complex patterns such as those generated by switchmode power supplies and triacs.AD8436 - Low Cost RMS to DC Convertor
There is an evaluation board available to study its performance.
Delivers true RMS or average rectified value of an AC input and Fast is settling at all input levels.It is an Accurate conversion with crest factors up to 10.
Typical application for frequencies as low as power line, and above. The recommended averaging, crest factor and LPF capacitor values are 10 μF, 0.1 μF and 3.3 μF.
- Accuracy: ±10 µV ± 0.5% of reading
- 100 µV rms to 3 V rms (8.5 V p-p) full-scale input
- 1 MHz for -3 dB (300 mV)
- 65 kHz for additional 1% error
- Zero converter dc output offset
- Low power: 300 µA typical at ±2.4 V