Plusivo DM501D - Battery Internal Resistance Measurement

And if we measure the current in this circuit.
The measured current in this figure is 3.280 mA.
Now, let us calculate the value of the resistor. We have a 9 V battery, the voltage on the LED is 1.886 V, so
the voltage on the resistor is:
9 𝑉 − 1. 886 𝑉 = 7. 114 𝑉
Now, let us use Ohm’s law:
𝑅 =
𝑉
𝐼
𝑅 =
7.114 𝑉
20 𝑚𝐴
= 355. 7 Ω
And the closest standard value is 330 Ω.
Now, let us build the circuit again using a 330 Ω resistor and measure the forward voltage again and the
current.
The measured voltage in this figure is 1.996 V DC
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Mastering the Art of Measurement (DM501D Digital Multimeter) r.01 www.plusivo.com