Error of Measurement . The result of a measurement minus the true value of the measurand. International Organization for Standardization, a worldwide federation of national standards bodies. National Conference of Standards Laboratories. The degree of agreement between two or more results on the same property of identical test material expressed as the repeatability or reproducibility of an instruments readings.
Precision is a quantitative concept.
Refractive Index . Traditional Refractometer . A hand-held device using lenses and prisms for measuring refractive index or a physical property directly related to refractive index. Abbe Refractometer . A high precision bench-top or laboratory instrument used to measure refractive index or a physical property directly related to refractive index.