A
conventional electrical unit (or
conventional unit where there is no risk of ambiguity) is a
unit of measurement in the field of
electricity which is based on the so-called "conventional values" of the
Josephson constant and the
von Klitzing constant agreed by the
International Committee for Weights and Measures (CIPM) in 1988. These units are very similar in scale to their corresponding
SI units, but are not identical because of their different definition. They are distinguished from the corresponding SI units by setting the symbol in italic typeface and adding a subscript "90" – e.g., the conventional volt has the symbol
V90 – as they came into international use on 1 January 1990.