Systematic errors

Systematic errors occur when an instrument is wrongly calibrated or there is some unknown factor affecting all readings. For example, if there is an unknown quantity of salt in a sample of 'distilled' water the conductivity will always be too high. Averaging more readings will give a more accurtate wrong value.

Systematic errors are not dealt with in simple lab exercises. For example, rulers could be checked with gage blocks but the time and expense are not considered worth the effort in teaching laboratories.

Students may assume that a manufacturer will not put marks on a scale that are meaningless. Analog meters and rulers are to be taken as accurate to within half the smallest scale division. The booklet that comes with digital meters contains information on the accuracy to be expected on different ranges.

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