Measuring the temperature of a reflective surface, such as that of a glass, metal or plastic product, is not the easiest of tasks. Lots of manufacturing companies could attest to that. We would be only too happy to explain how you can do this.
Inaccurate measurement due to reflection
A reflective surface absorbs not only the temperature of the product itself but also the ambient heat. This can cause the measurement to be higher on occasion. Consequently, the product (or semi-finished product) will have a different shape, strength or thickness than desired, none of which benefits its quality. By using a good infrared sensor that factors in this measurement error, you can prevent this from happening.
How an infrared sensor works
An infrared sensor (also called a thermographic camera or pyrometer) is capable of measuring the temperature of a surface without being in contact with it. It does so by capturing and storing the heat radiated from the object. This might sound simple; however, when you’re dealing with a highly reflective product, made from, say, metal or glass, the temperature reading will appear higher than it really is. That is why we need a correction: the emissivity factor.
The emissivity factor minimises the measurement error caused by reflected radiation, thus allowing accurate temperature recordings. Exactly what that factor is depends on the amount of reflected radiation from the surface. There are certain formulas available for this. The emissivity factor is easy to set using the built-in software or an electronics box so that the data is displayed correctly in one go.
No standard solution
Not all infrared sensors are suitable for measuring reflective surfaces. For example, if we are dealing with a glass surface, we need to take into account not only any reflection but also the transparency of the surface. Unfortunately, there is no off-the-peg answer to what the corrective factor should be and which infrared sensor is best suited for your application. It varies between objects, surroundings and applications. Also when we talk about other reflective surfaces such as metal wheels, glass bottles, plastic packaging materials, aluminium brackets, etc., we need to carry out tests at the production site to provide you with good measuring advice.
And we are always happy to give good measuring advice! Please contact infrared specialist Maaike Godschalk without obligation. She will be happy to provide you with further assistance!