A 50-µA meter movement has an rM of 1000 Ω. What RS is needed to extend the range to 500 µA?

Question

A 50-[latex]\mu[/latex]A meter movement has an [latex]r_M[/latex] of 1000[latex]\Omega[/latex]. What [latex]R_S[/latex] is needed to extend the range to 500 [latex]\mu[/latex]A?

Accepted Answer

The shunt current [latex]I_S[/latex] is 500 _ 50, or 450[latex]\mu[/latex]A. Then

[latex]R_S=\frac{V_M}{I_S} \[0.5cm] =\frac{50\times 10^{-6} A\times 10^3\Omega}{450\times 10^{-6}A} =\frac{50,000}{450}[/latex]

[latex]R_S=111.1\Omega[/latex]

Question 12.2: A 50-µA meter movement has an rM of 1000 Ω. What RS is neede...

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