fundamental interval

fundamental interval

[¦fən·də¦men·təl ′int·ər·vəl] (thermodynamics) The value arbitrarily assigned to the difference in temperature between two fixed points (such as the ice point and steam point) on a temperature scale, in order to define the scale. The difference between the values recorded by a thermometer at two fixed points; for example, the difference between the resistances recorded by a resistance thermometer at the ice point and steam point.