Making reliable measurements
Careful technique reduces random variation, parallax and avoidable systematic error.
Repeat readings, identify anomalies, average consistent results and increase measured intervals where possible.
By the end of this lesson, you can:
- read analogue and digital instruments correctly;
- reduce parallax;
- use repeated readings and averages;
- measure small effects using multiples.
Reading scales
View an analogue scale normally to avoid parallax. Record every measured value to the instrument's precision, including trailing zeros when meaningful.
Repeat and average
Repeat measurements when random variation is present. Identify anomalous readings with evidence, then calculate a mean from consistent results.
Measure multiples
Improve percentage precision by timing many oscillations or measuring several repeated spacings, then divide by the number.
WORKED EXAMPLEReveal method
If 20 oscillations take 31.6 s, the period is 1.58 s. Timing one oscillation would have much larger percentage timing uncertainty.
Try another worked problem
Attempt the question yourself, then reveal the examiner-style solution when you are ready.
Timing reliability
Why time 20 oscillations rather than one?
CHECK YOUR ANSWERReveal solution
The same reaction-time uncertainty is a smaller percentage of the longer total interval.
Mastery check
Timing 20 oscillations instead of one mainly reduces the percentage uncertainty due to: