Accuracy vs Inaccuracy

Instrument engineer usually finds term ‘accuracy’ in some catalog and ‘inaccuracy’ in some others. To know whether there is a difference between both of them, try to understand the meaning of each.

The accuracy of an instrument is a measure of how close the output reading of the instrument to the correct value. Inaccuracy does mean similar i.e. the degree to which a measurement might be error from the correct value.

Let’s take a measurement device with 0-100 psig range and 2% of span accuracy. It does not mean the error will be 98 psig, instead the error will not be more than 2 psig. Although in this condition the term inaccuracy could be more suitable, yet most industry practice express the error reading from correct value as accuracy. The term accuracy and inaccuracy is often used interchangeably.