Published Online: 12 OCT 2012
Copyright © 2003 by John Wiley & Sons, Inc. All rights reserved.
Characterization of Materials
How to Cite
Dollimore, D. and Samuels, A. C. 2012. Thermometry. Characterization of Materials. 1–10.
- Published Online: 12 OCT 2012
Thermometry is the science of measuring temperature, and thermometers are the instruments used to measure temperature. Temperature must be regarded as the scientific measure of “hotness” or “coldness.” This article is concerned with the measurement of temperatures in materials of interest to materials science, and the notion of temperature is thus limited in this discussion to that which applies to materials in the solid, liquid, or gas state (as opposed to the so-called temperature associated with ion gases and plasmas, which is no longer limited to a measure of the internal kinetic energy of the constituent atoms).
A brief excursion into the history of temperature measurement will reveal that measurement of temperature actually preceded the modern definition of temperature and a temperature scale.
The simple expedient of sealing the instrument so that the liquid and gas were contained in the tube really marks the invention of a glass thermometer. By making the diameter of the tube small, so that the volume of the gas was considerably reduced, the liquid dilation in these sealed instruments could be used to indicate the temperature. Fahrenheit eventually substituted mercury for the “spirits of wine” earlier used as the working liquid fluid, because mercury's thermal expansion with temperature is more nearly linear. Temperature scales were then invented using two selected fixed points—usually the ice point and the blood point or the ice point and the boiling point.
The starting point for the thermodynamic treatment of temperature is to state that it is a property that determines in which direction energy will flow when it is in contact with another object. Heat flows from a higher temperature object to a lower temperature object. When two objects have the same temperature, there is no flow of heat between them and the objects are said to be in thermal equilibrium. Heat transfer is an important consideration for many materials engineering applications, and thermal conductivity measurements rely on accurate and precise temperature measurement and control. Development of the International Temperature Scale of 1990 is detailed. Various types of thermometer are discussed as well as the need, sometimes, to control the temperature. Recent developments in the measurement of temperature and thermal properties at the microscopic scale are also reviewed.
- thermodynamic temperature scale;
- international temperature scale of 1990;
- fixed points;
- thermometer types;
- temperature control;