Calibration and verification of thermometers. General information and description of the instruments

Temperature is one of the most frequently measured physical quantities, as it is a major influencing parameter in many industrial production processes. In addition, virtually all other macroscopic physical quantities of interest to industry and research are more or less strongly influenced by temperature. Temperature measurements are used in all areas of the company: research and development, production, control, safety and packaging. All areas of industrial activity are concerned, from automotive production to the transport of biological substances.

The term "thermometer" is often used to designate either a temperature measurement chain (or thermometer chain) or a temperature sensor. To avoid any ambiguity, it is preferable to reserve this term for the designation of a complete chain.

Temperature sensors come in all shapes and sizes. From the first liquid column thermometer invented by the Duke of Tuscany in 1654, to the emerging range of stand-alone sensors with wireless transmission to a host receiver, there has been a great deal of evolution! Temperature sensors deliver information relating to a physical quantity (resistance, volume, voltage, etc.) which is associated with a temperature value through calibration.

In this article, we will confine ourselves to the field of contact thermometry: i.e. temperature sensors that are placed directly in contact with the calibration medium or the medium whose temperature is to be determined. We will also restrict this document to sensors used in the temperature range from 83.8058 K to 2041.35 K. This range covers most industrial needs.

The temperature chains available on the market incorporate very different sensor technologies. Each type of sensor is associated with specific precautions for use, as well as influencing parameters which will affect the final result. Most temperature chains supply temperature information directly, but users should be aware of the nature of the input data supplied by the sensor integrated into the chain (electrical resistance, voltage, etc.), and how this data is transformed into a temperature value.

This article does not deal with devices for measuring temperature by analyzing radiation: on this subject, the reader is referred to the article on optical pyrometry [R 2 610] in this treatise.

This article does not deal with cryogenic probes used below 83.8058 K.

This article does not deal with surface temperature sensors.