| 摘要 |
A potential input circuit and a current input circuit, each having a transformer therein, receives the input information from the power line for which the true electrical power is to be measured. The scaled output from the potential input circuit, and a triangle wave signal from a generator therefor are coupled to a comparator (level crossing detector) employing an open loop operational amplifier (op amp) having an output controlling electronic switches to gate the current transformer secondary current, with a duty ratio proportional to voltage amplitude and polarity. The gated output of the current transformer is filtered and coupled through an amplifier, or directly, to an external load. The filtered output is in the form of a linear direct current analog of true power in the power line.
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