Accuracy and precision are paramount when specifying sensors. The two terms are often used interchangeably, but there are fundamental differences between them. Accuracy, a qualitative concept, indicates the proximity of measurement results to the true value; precision reflects the repeatability or reproducibility of the measurement.
ISO 3534-1:2006 defines precision to mean the closeness of agreement between independent test results obtained under stipulated conditions, and views the concept of precision as encompassing both repeatability and reproducibility. The standard defines repeatability as precision under repeatable conditions, and reproducibility as precision under reproducible conditions.
Precision, accuracy, repeatability, reproducibility, variability and uncertainty represent qualitative concepts and thus should be applied with care. The precision of an instrument reflects the number of significant digits in a reading; the accuracy of an instrument reflects how close the reading is to the true value being measured. An accurate instrument is not necessarily precise, and instruments are often precise but far from accurate.