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. A conversion factor is a fraction that relates one unit to another. Multiplying a measurement by a conversion factor changes the units of the measurement. The SI unit of electric charge, equal to the amount of charge delivered by a current of 1 ampere running for 1 second.