Key components

The Therm-O-Matic® Surface
Inspection system


Short description of key components

This inspection principle/method was invented by Elkem Technology. The technology required to make this work was at that time not available on the civilian market. In cooperation with a company with good knowledge of military IR technology and real time signal processing technology Elkem developed an IR line scanner, signal processor, analyzing software and detection algorithms. A one-sided prototype was built and used to explore the possibilities and limitations of this new inspection method.Thousands of test runs in a one-sided proto type were used to gain the know-how and to make live tests in potential customers own inspection lines. The technical information gained from these tests enabled us to design the first Infra-Red Surface Inspection System for inspection of hot rolled billets and bars. The first Therm-O-Matic® was delivered to Krupp Südwestfahlen and went directly into production at start-up.The Therm-O-Matic® system has been further developed over years by IRTech to take advantage of the possibilities of this completely new inspection method with the latest technology in image processing.


A high frequency current is induced in the surface when the billet or bar runs through a circular coil connected to a HF generator. The induced current heats the skin of the surface. Defects open to the surface forces the current to go beneath the defects and extend the length of the induced current path. A local rise in temperature Δt corresponds to the length of the detour. The Δt is therefore also equal to the depth of the defect. Highly sensitive infrared scanners record an image of the surface temperature. The temperature image is analyzed by signal processors detecting, measuring and comparing the local Δt with the selectable and variable depth thresholds. Defects deeper than the depth threshold are marked true to position by paint guns.

HF System

All the system uses the same generator and heating unit (coil) perfectly adapted to our purpose. The induction coil is powered by a HF-generator operating at a frequency high enough to give the induced current a penetration depth smaller than 1/10 of a mm. 


The IR scanner is the most important component in Therm-O-Matic®.
The line scanner is specially developed with functions only required for this application. The components are according to military specfications with high reliability. More than 100 units of the IR-scanner have been built. Some of them have been running continuously for more than 25 years, and still operates with the same performance today. We are very proud of the track record of our scanner.