Temperature > 09 - International Temperature Scale

To better express the laws of thermodynamics, a scale was created based on the phenomenon of change in the physical state of pure substances, which occurs under unique conditions of temperature and pressure. These are called fixed temperature points.

This scale is called IPTS - International Practical Temperature Scale. The first scale appeared in 1920, modified in 1948 (IPTS-48). In 1960, more modifications were made and in 1968 a new International Practical Temperature Scale was published (IPTS-68).

The still current IPTS-68 covers a range from -259.34 to 1064.34ºC based on the melting, boiling and triple points of certain pure substances, such as the melting point of some pure metals.

The latest version was adopted in 1990 by the Bureau International de Poids et Mesures (BIPM), called the International Temperature Scale of 1990 (ITS-90), and is the one that best agrees with the thermodynamic temperature scale.

International Norms and Standards

With the different technological development in different countries, a series of norms and standards have been created, each one serving a given region.

The most important are:

ISA - AMERICAN
DIN - GERMAN
JIS - JAPANESE
BS - ENGLISH
UNI - ITALIAN

In order to meet the different technical specifications in the area of ​​thermometry, efforts are increasingly being made to unify these standards. To this end, the International Electrotechnical Commission (IEC) has been working with the countries involved in this normative process, not only to obtain more complete and improved standards, but also to provide means for the internationalization of the instrumentation market related to thermocouples.

As one of the participants in this commission, Brazil, through the Brazilian Association of Technical Standards (ABNT), is also directly interested in the development of this subject and has been adopting these specifications as Brazilian Technical Standards.