Josephson constant 2

The inverse of the flux quantum is called the Josephson constant (denoted: `K_J`), and is the constant of proportionality of the Josephson effect, relating the potential difference across a Josephson junction to the frequency of the irradiation. The Josephson effect is very widely used to provide a standard for high-precision measurements of potential difference, which (since 1990) have been related to the fixed "conventional" value of the Josephson constant (denoted: `K_(J-90)`).  This constant is expressed in units of Hertz per volt (Hz/V).