Accuracy is the correctness of a single measurement. The accuracy of a measurement is assessed by comparing the measurement with the true or accepted value, based on evidence independent of the measurement. The SI unit of electric current , equal to flow of 1 coulomb of charge per second. An ampere is the amount of current necessary to produce a force of 0.2 micronewtons per meter between two arbitrarily long, arbitrarily thin wires, placed parallel in a vacuum and exactly 1 m apart. A non- SI unit of length used to express wavelengths of light, bond lengths, and molecular sizes.
Base units are units that are fundamental building blocks in a system of measurement.
There are seven base units in the SI system. Calibration is correcting a measuring instrument by measuring values whose true values are known. Calibration minimizes systematic error . Compare with SI . An older metric system of units that uses centimeters, grams, and seconds as base units.