Temperature scientists measure temperature using the Celsius scale and thermodynamic temperature using the Kelvin scale, which is the Celsius scale offset so that its null point is = , or absolute zero. Many engineering fields in the U.S., notably high-tech and US federal specifications (civil and military), also use the Kelvin and Celsius scales. Other engineering fields in the U.S. also rely upon the Rankine scale (a shifted Fahrenheit scale) when working in thermodynamic-related disciplines such as combustion. The basic unit of temperature in the International System of Units (SI) is the kelvin. It has the symbol K. For everyday applications,
Wedgwood scale The scale was divided into 240 equidistant parts. The unheated piece of clay would fit the 0.5-inch gap giving the zero temperature reading. After annealing, the clay cylinder would shrink and fit somewhere in between the left and right ends of the bars, and the temperature could be read from the scales on the bars. The origin (0°) on Wedgwood scale was set at the onset temperature of red heat, . The scale had 240 steps of and extended up to . Wedgwood tried to compare his scale with other scales by measuring the expansion of silver as a function