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FIGURE 13.25 Theoretical prediction of back-surface temperature rise.
FIGURE 13.26 Schematic diagram of experimental thermal imaging apparatus.

thermal diffusivity measurement determined by this method can be calibrated with standards.

A typical experimental system used for obtaining diffusivity measurements over a predetermined area is shown in Fig. 13.26. The apparatus includes an infrared (IR) camera that consists of a focal-plane array of 256 x 256 InSb detectors, a 200-MHz Pentium-based personal computer (PC) equipped with a digital frame grabber, a flash lamp system for the thermal impulse, a function generator to operate the camera, and a dual-timing-trigger circuit for the camera and external trigger control. An analog video system is used to monitor the experiments. Processing time to measure a typical diffusivity image with 256 x 256 pixels ranges from 8 to 20 s, depending on the number of frames taken.

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