Measuring Instruments & Errors — A/L Physics

Systematic Error An error that is constant or changes in a predictable way under repeated measurements. Systematic errors arise from faulty calibration, zero offset, or environmental effects. They cause all readings to be consistently too high or too low. Example: A ruler with a worn zero edge always gives readings 0.5 mm too large.

Random Error An error that varies unpredictably in magnitude and sign from one measurement to the next. Random errors are due to limitations in reading scales, slight variations in experimental conditions, or human reaction time. They can be reduced by taking many readings and averaging. Example: Timing a pendulum swing with a stopwatch; each trial gives a slightly different time due to reaction time.