RMS to DC Converter series. To measure the RMS value of alternating voltage of a converter is needed to produce accurate RMS value of the input alternating pure as DC output. With a simple sinewave input RMS voltage can only be calculated as 0.707 times the peak AC voltage, but with a complex waveform calculation is hardly easy. RMS value is defined as a DC voltage which will give the same heating effect in a resistor as an alternating voltage. LTC 1966 from Linear Technology uses a new form of delta-sigma conversion and is designed for battery operation, only draw 170μA of supply. The new technique is accurate to 0.02% between 50 mV and 350 mV and very linear. It can operate from 50 Hz to 1 kHz (with an error 0.25%) and up to 6 kHz with an error of 1%.
Anyway, for more details, please refer to the schematic drawings and learn the RMS to DC Converter circuit below.
The following are important things to note from the RMS to DC Converter series. Input voltage range on the differential inputs IN1 and IN2 to the additional input supply rail, and non-symmetrical circuit shown here at the IN1 voltage can swing between 0 V and the supply voltage. If the signal to be measured is AC only, the other coupling capacitors are required. Input impedance is some megaohm. Output voltage at the OUT pin can be offset by applying a DC voltage to pin OUT RTN. This is especially helpful when using the device with a multimeter as LCD IC 7106. A capacitor is further connected to the output that is charged to the voltage required by the switched-capacitor circuit in the converter. Capacitors required is ten times smaller than that demanded by the previous RMS to DC converter designs. This allows small RMS to DC converter to be built using only four components
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