Two currents from different sources flow in opposite directions through a resistor. I1 is measured
as 79 mA on a 100 mA analog scale with an accuracy of ±3% of full scale .I2 is determined as
31 mA and is measured on a digital instrument with ±100 𝜇𝐴 accuracy. Infer the accuracy of
measured current in the resistor.
To infer the accuracy of the measured current in the resistor, we need to consider the accuracy of both measurements (I1 and I2) and calculate the overall accuracy.
1. For I1:
- The measured value on the analog scale is 79 mA.
- The accuracy of the analog scale is ±3% of full scale.
- The full scale of the analog instrument is 100 mA.
To calculate the accuracy of the measurement, we can use the formula:
Accuracy = ±(accuracy percentage / 100) * full scale
Accuracy = ±(3/100) * 100 mA
Accuracy = ±3 mA
Therefore, the accuracy of the measured value of I1 is ±3 mA.
2. For I2:
- The measured value on the digital instrument is 31 mA.
- The accuracy of the digital instrument is ±100 𝜇A.
Therefore, the accuracy of the measured value of I2 is ±100 𝜇A.
To calculate the overall accuracy, we need to consider the worst-case scenario, which means we take the larger of the two accuracies:
Overall Accuracy = maximum(±3 mA, ±100 𝜇A)
Since the two values are in different units, we need to convert the accuracy of 100 𝜇A to mA:
1 mA = 1000 𝜇A
Therefore, 100 𝜇A = 0.1 mA
Comparing the two accuracies, we have:
±3 mA > ±0.1 mA
Therefore, the overall accuracy of the measured current in the resistor is ±3 mA.