Manganese-copper shunt is connected to three wires instead of directly grounding a section of the voltage source
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There is almost no current on these two leads, and there is no voltage drop. The signal sampled by the meter current is the voltage drop of the current to be measured on the copper. The current (supply current) consumed by the meter only passes through the red lead. I The current to be measured The supply current passes through the yellow lead, so there is a certain voltage drop on it