| 摘要 |
The method involves producing a measurement signal which is proportional to an effective power emerging from an AC voltage and a corresponding current, whereby the voltage (U(t)) and the current (I(t)) are sampled by device of a sample-and-hold circuit (1,2) with the same clock, and are converted in respective A/D converters (3, 4) into corresponding digital values (U(ntA), I(ntA)). The corresponding digital voltage and current values are multiplied with each other to form digital product values (f(ntA)) which are subsequently digitally filtered in a calculation unit (25) with a non-recursive digital filter (FIR) formed as a low-pass filter, to form the measurement signal (S). The product values are filtered before their supply to the calculation unit, at least once in a low-pass pre-filter (7,15) and are subsequently subjected to a sampling rate reduction (10,20).
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