Lake Shore Model 370 AC Resistance Bridge User’s Manual
APPENDIX B
TEMPERATURE SCALES
B1.0 DEFINITION
Temperature is a fundamental unit of measurement which describes the kinetic and potential energies of the atoms and
molecules of bodies. When the energies and velocities of the molecules in a body are increased, the temperature is
increased whether the body is a solid, liquid, or gas. Thermometers are used to measure temperature. The temperature
scale is based on the temperature at which ice, liquid water, and water vapor are all in equilibrium. This temperature is
called the triple point of water and is assigned the value 0 °C, 32 °F, and 273.15 K. These three temperature scales are
defined as follows:
Celsius.
Abbreviation: °C. A temperature scale that registers the freezing point of water as 0 °C and the boiling point as
100 °C under normal atmospheric pressure. Formerly known as “Centigrade.” Originally devised by Anders Celsius
(1701
–
1744), a Swedish astronomer.
Fahrenheit.
Abbreviation: °F. A temperature scale that registers the freezing point of water as 32 °F and the boiling
point as 212 °F under normal atmospheric pressure. Originally devised by Gabriel Fahrenheit (1686
–
1736), a
German physicist residing in Holland; developed use of mercury in thermometry.
Kelvin.
Abbreviation: K. An absolute scale of temperature, the zero point of which is approximately –273.15°C.
Scale units are equal in magnitude to Celsius degrees. Originally devised by Lord Kelvin, William Thompson,
(1824
–
1907), a British physicist, mathematician, and inventor.
B2.0 COMPARISON
The three temperature scales are graphically compared in Figure B-1.
Boiling point of water
Freezing point of water
Absolute zero
kelvin
Celsius
Fahrenheit
0 K
273.15 K
373.15 K
273.15 °C
0 °C
100 °C
459.67 °F
32 °F
212 °F
Figure B-1. Temperature Scale Comparison
B3.0 CONVERSIONS
To convert Fahrenheit to Celsius: subtract 32 from °F then divide by 1.8, or:
°C = (°F – 32) ÷ 1.8
To convert Celsius to Fahrenheit: multiply °C by 1.8 then add 32, or:
°F = (1.8 × °C) + 32
To convert Fahrenheit to Kelvin, first convert °F to °C, then add 273.15.
To convert Celsius to Kelvin, add 273.15.
Temperature Scales
B-1
