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Understanding the Importance of 'HOT SPOT' Measurement in Non-Contact Temperature Measurement Applications

In applications for non-contact temperature measurement, the term "HOT-SPOT measurement" is commonly used to not only recognize and measure "hot spots" or areas of high temperature, but also detect cold, cooler areas and show their distribution. In principle, the temperature of an object in a process can be detected and measured in three ways:

Using a PYROMETER – which detects the object temperature at one spot. This means it is a temperature measurement at one spot over time (1D).

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The temperature measurement relates to a fixed point - HOT SPOT - of a non-moving object over time, e.g. in applications in which a certain area is heated, where the temperature must be determined and the process must be controlled. This results in a current temperature trend, which can be used to control the heating process. With moving objects, such as heated blocks that are fed to hot forming or in rolling processes in which the rolling stock or strip is moved in the rolling direction, you also get a temperature trend, but this then refers to the line created from the measuring point, which is produced by the movement of the rolling stock.

Using an (IR) LINE SCANNER – This method detects the temperature along a measuring line (profile). Each scan-line consists of 1,000 individual measuring points (samples) and thus generate an exact temperature profile. With measuring frequencies of up to 150 lines per second - corresponding to 150,000 measuring points per second, fast-moving objects, e.g. in rolling processes, result in an accurate and continuous measurement of the temperature distribution. 

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In addition to the complete profile recording, this also includes the recording of hotter and cooler points perpendicular to the direction of movement and thus provides information about the uniformity of the temperature distribution. The measured lines (scans) are then added to one another and thus result in a continuous picture of temperature profiles over time (for non-moving objects) or temperature profiles over time and location (for moving objects). With moving objects, this results in a complete thermal image and accurate image of the temperature distribution – e.g. a complete coil in the rolling process.

Using a THERMAL IMAGER – A well-known type of "HOT-SPOT measurement" is the use of a typical portable thermal imaging camera for building thermography to find hot/cold bridges and leaks on the building. In the field of industrial thermal imaging, hot areas are detected on moved or non-moved objects, detecting the object HOT SPOTS and the whole temperature distribution. This method can be used in the following ways:

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In processes such as ladle and kiln monitoring, industrial thermal imaging is used to safely detect critical surface temperatures – or HOT SPOTS – which might cause damage to such a ladle or kiln and to avoid dangerous breakthroughs at a very early stage, examples include Billet Reheat Furnace, Walking Beam Furnace and Tube Reformer Furnace.

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Market leading furnace thermal imaging systems are used to continuously (24/7) monitor and measure the internal furnace temperatures, temperature distributions, stock temperatures and detect HOT SPOTS or cold LEAKS to control and optimize the furnace process, reduce energy costs and emissions across their fully radiometric calibrated thermal image.

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