Brands
Vishay Measurements Group
Interactive Guide
Tech Notes
TN-513
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Measurement of Thermal
Expansion Coefficient
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(...continued)
The principle of measuring expansion coefficients with strain gages then becomes evident from the previous illustration , since the rotation from one thermal output curve to the other is due only to the difference in thermal expansion properties between the materials represented by the two curves. An algebraic demonstration of the principle can be obtained by rewriting Eq. ( 513.4 ) twice; once for the gage installed on a specimen of the test material of unknown expansion coefficient 
, and again for the same type of gage installed on a
standard reference material with a known expansion
coefficient
:
Thus, the difference in expansion coefficients, referred to a particular temperature range, is equal to the unit difference in thermal output for the same change in temperature. Although this technique for measuring expansion coefficients is widely applicable, and often the most practical approach, there is relatively little information about it in the technical literature. Representative applications are described in the bibliography to this publication (Ref. 4 and 5 ). 
Page 5 of 24 |
(513.5a)
(513.5b)
