Once the counter and stopwatch are stopped, compare the two readings. Use
the equation Δt/T to get the results, where Δt is the difference between the
counter and stopwatch displays, and T is the length of the measurement run. For
example, if Δt = 100 ms and T = 1 hour, the time uncertainty is 0.1 s / 3600 s or
roughly 2.8 × 10-5 (0.0028 %).