Laser-spot lock-in thermography with a non-research-grade thermal camera: From thermal diffusivity measurements to visualizing free convection

Abstract

The widespread use of Lock-in Thermography (LIT) has been hindered by the high cost of the thermographic cameras available for such applications. We show that a low-cost thermographic camera (we used the QIANLI MEGA-IDEA Super iR Cam 2S) can be straightforwardly used in advanced applications, particularly for measuring the thermal diffusivity of solids using the Laser Spot LIT Technique and the Slope Method. The results of measurements performed in test samples were compared with those obtained using the FLIR SC5000 research-grade camera, whose usefulness for this kind of application has been demonstrated before. The Super iR Cam 2S is almost two orders of magnitude cheaper than the FLIR SC5000 but has an inferior performance. However, a good agreement between the thermal diffusivities of materials, with values between 10 and 100 mm2/s, obtained using both cameras and those reported in the literature demonstrates inexpensive instrumentation usefulness for conducting high-quality research work. The visualization of cracks between samples with different diffusivities was demonstrated too. For the first time, we also show the possibility of using Laser Spot LIT to directly observe a convective effect in a fluid layer closest to the sample’s surface.