Bimetal thermometers – applications Among the many categories of thermometers, the bimetallic ones offer a guarantee of measurement and reliability in all those fields where mercury is prohibited, such as pharmaceuticals, food or oil plants.

They also offer good performance and immediate detection and at the same time easy cleaning and maintenance.

The choice very often on this type of thermometers is based on the use we will make, usually of detection based on the internal expansion of the thermometric materials.

The operating principle is based on the different expansion of the materials as a response to heat; in this case the Bimetal Thermometer is represented by two metal strips connected together . As the two blades are permanently bound, once exposed to temperature variations, they tend to move by flexing and arching, following a particular curve.

This movement generates a rotation of the blades on themselves, which is indicated by the graduated scale on the dial.

The structure of the thermometer is formed by a quadrant to which a spring is fixed which acts as a thermometric element, it is introduced into a bulb to which one end is fixed.

The other hand remains free and connected to the index generating a thermometric measuring range between -70 degrees and + 600 ° C.

They are used in many industrial processing sectors , from the chemical and petrochemical sector where thermometers must by law not contain mercury or other liquid substances. Where resistance and ease of reading are fundamental and essential characteristics to guarantee simple and fast readings.

Built in insulating and resistant materials, such as stainless steel , they guarantee a very high degree of protection, making them perfect for intense industrial use where the work environment is aggressive. The thermowell is connected to it, it has the function of protecting temperature sensors such as thermocouples, thermistors and bimetallic thermometers from damage caused by excessive pressure, material speed and corrosion. It also has the function of extending the service life of the sensor, and ensuring replacement without having to empty the system. Of different sections and different types of construction that can be tube or solid bar, in order to guarantee use in any type of industrial need In the construction of plants, thermometric wells combined with bimetallic thermometers are used for easy operation and the possibility of direct measurement.

In summary, we can define the bimetallic thermometer as the ideal instrument for use in the process industry, where vibrations and critical working environments for pressure and temperature require robust instruments that can be directly connected through sections and thermowells. They usually have circular and domed dials, in order to avoid parallax errors in the temperature reading and built with heat and pressure resistant materials such as stainless steel. 

They are also used in civil applications, such as boilers or steam accumulators, where detection accuracy is not the main characteristic required.

From civil and industrial air conditioning systems, bimetallic thermometers base their strength on the simplicity of the letter and on the operating principle, that is the thermal expansion of the lamellae that make up the heart of the measuring system.

Depending on the degree of protection (IP), thermometers can be used in various industrial sectors from textiles to petrochemicals, and gas transformation. Combined with viscous dissipating liquids, they can also be used in environments where there are strong vibrations and strong pressures.


Resistance, low maintenance cost , ease of reading: these are the characteristics of bimetallic thermometers , which only allow readings on site, limiting their civil use. In industrial plants it is important to guarantee: continuity of reading, ease of installation, and if necessary the possibility of replacing it with a loaded system, always guaranteeing optimal performance even in industrially demanding environments.