4.3.1 Voltage and Current Signals
The SD24 converter has a fully differential input and, therefore, no added dc offset is needed to precondition a signal, which is the case with most single-ended converters.
The output of the SD24 is a signed integer. Any stray dc offset value is removed independently for V and I by subtracting a long-term dc tracking filter's output from each SD24 sample. This long-term dc tracking filter is synchronized to the mains cycle to yield a stable output.
The resulting instantaneous voltage and current samples are used to generate the following information:
• Accumulated squared values of voltage and current for VRMS and IRMS calculations.
• Accumulated energy samples to calculate active energy.
• Accumulated energy samples with current and 90° phase shifted voltage to calculate reactive energy. These accumulated values are processed by the foreground process.