Types of errors

Different types of errors in measurements

1. Errors in Measurement System

2. Definition An error may be defined as the difference between the measured value and the actual/true value. The actual/true value is the average value of an infinite number of measured values. Measured value is the estimated value of true value that can be found by taking several measured values during an experiment.

3. Calculation of % error Absolute error = measured value - exact value = ׀ V A - V E ׀ Relative error = [measured value - exact value] / exact value = ׀ V A - V E / V E ׀ Percentage error = [measured value - exact value] / exact value x 100 % Percentage error = ׀ V A - V E / V E ׀ × 100%

4. Types of Errors in Measurement System

5. Gross Errors Gross errors are caused by mistake in using instruments or meters, calculating measurement and recording data results . (human errors)   Such errors may end up in calculation of the final results, thus deviating results.

6. Systematic error s Systematic errors occur due to fault in the measuring device. Usually they are called as Zero Error – a positive or negative error. These errors can be removed by correcting the measurement device.

7. Systematic errors are classified into Observational Errors: These occur due to wrong observations or reading in the instruments . (most common parallax error) Environmental Errors: These occur due to some external conditions of the instrument . (change in te mperature, humidity etc.) Instrumental Errors: These occur due to wrong construction of the measuring instruments .

8. Instrumental errors may occur due to : Hysteresis or friction. Loading effect and Misuse of the instruments.

9. Random errors Random errors are caused by the sudden change in experimental conditions. These errors are due to unknown causes. They are generally accumulation of a large number of small effects and may be of real concern. These errors can be analysed statistically. Noise can cause random errors in measurements. Hence, it is important to know the types of errors and minimise them so that measured data is interpreted properly.

10. The End