Selection of Instruments (Metrology)

The important characteristics to be considered in selection of an instrument are its measur-
ing range, accuracy and precision. Usually accuracy is poor at the lower end of scale which should
be avoided. In such a situation, where accurate measurement is required throughout full range,
two instruments with different ranges may be used, one for lower range and other for full range.
The precision of instrument is very important feature since it should give repeatable readings which
is possible with precise instrument. If an instrument is precise then accuracy can be taken care of
by proper calibration of the instrument. It may be mentioned that accuracy is affected by systematic
errors which can be accounted for.
Resolution or sensitivity, i.e. discrimination or relation between the movement of pointer
and corresponding change in the measured quantity is also important aspect. It represents a
smallest change in the measured quantity which produces a perceptible movement of the pointer.

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