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Non-contact temperature monitoring in harsh environments - BST

Temperature is critical in many industrial processes and traditionally thermocouples or IR thermometers are often used. In particularly demanding applications, the established technologies are not sufficient.

RISE is developing a new fiber optic method for non-contact, continuous monitoring of temperature in demanding environments.

Non-contact temperature measurement for steel and process industries.

The process industry, and specifically the steel industry, has a pronounced need for new improved solutions for temperature measurements in really demanding environments. In many of these environments, conventional IR thermometers do not work, so you have to rely on disposable thermocouples that give temperature in discrete measuring points over time, limiting the possibilities for good process control.

In collaboration with the Swedish steel and process industry, RISE has developed a new method for non-contact continuous temperature measurement. The method is based on IR thermometry, but unlike commercial IR thermometers, the method can better handle environments with disturbances from e.g. dust and dust or varying emissivity. The fact that the technology is fiber optic enables the use in applications where it is not possible to have a clear view into the process.

The technology has come to be known as BST, 'broadband spectral thermometer'.

The BST system uses the heat radiation to estimate the temperature. Since many industrial processes are hidden or difficult to access for measuring equipment, fiber optics here is a critical enabling technology to be able to collect and direct the heat radiation to the instrumentation. The BST system often uses a specially designed 'lance' equipped with optical fiber to 'look' at the melt and collect optical radiation.

The optical spectrum to be analyzed contains several different disturbances that BST takes into account.

Unlike conventional IR thermometers that only use a few discrete wavelengths, the BST system uses a wide range of wavelengths. This entire spectrum taken from the process radiation is analyzed and treated by smart algorithms and this is exactly what makes the technology more stable and less sensitive to interference than conventional IR thermometers.

In addition to the temperature, the optical spectrum collected also contains valuable information such as the presence of slag or alkalis. 

The BST technology has been developed in previous projects with funding from, among others, Vinnova and the participating industry, and the system has been verified in industrial trials in several Swedish steel plants and other process industries.

The solution is now in a commercialization phase, where Agellis RHI Magnesita is further developing the technology together with selected key customers and RISE.


Project name

Temperature monitoring in steel industry



RISE role in project

Project management, Development

Project start




Agellis RHI Magnesita, RISE Fiber optics


Project members

Supports the UN sustainability goals

9. Industry, innovation and infrastructure