To display power, a meter measures various voltages and currents in a
circuit. For two-wire, single phase AC, voltage is measured line-line (or line-neutral), either directly or using a potential transformer. Line current is measured directly or through a current transformer, as shown in the diagram. The combination of one voltage measurement and one current measurement means this meter has one
element. A 3-wire, single phase AC
circuit requires two voltage measurements (L1-N & L2-N...
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