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Proceedings Paper

Measurement limits in flash thermography
Author(s): Steven M. Shepard; James R. Lhota; Tasdiq Ahmed
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Paper Abstract

Although active thermography has traditionally been regarded as a qualitative NDT method, its potential for quantitative measurement of thermophysical properties including wall thickness, flaw size and depth, thermal diffusivity or effusivity has been the subject of numerous investigations. Enabled by improvements in IR camera technology and fast, abundant and inexpensive computing power for advanced signal processing, measurement results have been reported using a variety of excitation and signal processing schemes. Results are often presented as a correlation between thermography data and nominal properties or independent measurements by another "validated" method. However, given the diffusion mechanism that underlies thermography, and the quantization and sampling conditions implicit in using an IR camera as a temperature sensor, there are definite limits to what can be achieved in a thermography measurement. While many benefits can be achieved with improved instrumentation, efficient energy insertion or optimized signal processing, ultimately, the limits imposed by diffusion and instrumentation take precedence, and cannot be circumvented. In this paper, the effects of camera frame rate and sensitivity on measurement of the thickness of a slab are examined, using basic 1-dimensional diffusion approximations.

Paper Details

Date Published: 22 April 2009
PDF: 7 pages
Proc. SPIE 7299, Thermosense XXXI, 72990T (22 April 2009); doi: 10.1117/12.820062
Show Author Affiliations
Steven M. Shepard, Thermal Wave Imaging, Inc. (United States)
James R. Lhota, Thermal Wave Imaging, Inc. (United States)
Tasdiq Ahmed, Thermal Wave Imaging, Inc. (United States)

Published in SPIE Proceedings Vol. 7299:
Thermosense XXXI
Douglas D. Burleigh; Ralph B. Dinwiddie, Editor(s)

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