Let’s consider the example of Ohm’s Law P = I2R, where P is power, I is current, and R equals resistance. The uncertainty uc in the power measurement is given by the following equation:
gives the uncertainty in the current, u.
A set of measurements produce the following estimate of the Measurands (current and resistance) during a calibration test.
I = 15.000 Amps
R = 1.0500 Ω
Variance(I) = 8.28E-06 A2
Variance(R) = 4.6888E-09 Ω2
Covariance(I, R) = -5.2E-09 A Ω
The uncertainty in the power measurement, P, can be computed based on the following equation:
Use the values above to solve for .
The correct value for is:
The correct answer is d.
Taking the square root, the Standard Uncertainty (uc) on the Power, P, = ±0.0095 Watts.