Moving-coil meter measures low-level currents

Posted on Nov 13, 2012

Large moving-coil meters may require significant amounts of current for full-scale deflection, and using a shunt resistor may prove impractical when the meter current is larger than the current you are measuring. You can solve the problem by driving the meter from a separate power supply (Figure 1). In this example, an 8-in. moving-coil meter that requires 15 mA for full-scale deflection displays a current range of 0 to 1A dc. This technique can also simplify specifying or fabricating shunt resistors for custom current ranges.

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