Question

A digital meter has an accuracy of ±1%.
The meter is used to measure the current in an electrical circuit.
The reading on the meter varies between 3.04A and 3.08A.
What is the value of the current, with its uncertainty?
A (3.06 ± 0.02)A
B (3.06 ± 0.04)A
C (3.06 ± 0.05)A
D (3.06 ± 0.07)A

Answer 1

Mean value of the measurement

I̅ = (3,08+3,04)/2 = 3,06 A

Minimum value

Iₘᵢₙ = 3,04 - 3,04 x 1% =

Iₘᵢₙ = 3,04 - 0,03 = 3,01 A

Maximum value

Iₘₐₓ = 3,08 + 3,08 x 1%

Iₘₐₓ = 3,08 + 0,03 = 3,11 A

Uncertainty

ΔI̅ = (3,11 - 3,01)/2 = 0,05 A

The value of the current

I = I̅ ± ΔI̅

I = 3,06 ± 0,05 A