Errors in Measurement

• mo measurement is exact.All measurements will have some degree of error or uncertainty
• there are two main types of errors : -systematic errors ,-random errors

Systematic Errrors

-systematic errors are cumulative errors that can be compensated for,if the errors are known

-systematic errors in measurement result from

* an incorrect position of the zero point

*an incorrect calibration

-a zero error arises when the measuring instrument does not start from exactly zero

-zero errors are consistently present in every reading of a measurement so that the results obtained may be precise but lack in accuracy

-systematic errors explain why all readings taken are always larger or always smaller than the true value

-systematic errors cannot be elaminated by repeating the measurements and averaging out the results.It only can be elaminated or corrected if the measuring instruments are calibrated or adjusted frequently.

Random Errors

-random errors arise from unknown and unpredictable variations in condition,and will produce a different error every time you repeat the experiment.They may vary from observation to observation.

-random errors are caused by factors that are beyond the control of the observers.

-random errors may occur for a variety of reasons.They may be due to

*personal error such as human limitations if sight and touch

*lack of sensitivity.When there is an insignificant or small change,an instrument may not be able to respond to it or to indicate it or the observer may not be able to discern it

*natural errors such as changes in wind,temperature,humidity,refraction,magnetic field or gravity while the experiment is in progress.

*the use of a wrong technique of measurement such as applying excessive pressure when turning a screw gauge

-random errors can be minimised by reapiting the measurements several times and taking the average or mean value of the readings