Local Sources: Strain Measurement Errors

Local Sources

Strain at the molecular level is related to the relative spacing between atoms. The strain gage, of course, has finite stiffness and may locally reinforce the test part to which it is bonded. This reinforcement is ordinarily significant only for test materials with low elastic moduli such as plastics, and for thin specimens (Tech Note TN-505, Strain Gage Selection Criteria, Procedures, Recommendations ).

The strain in the test part can also be affected by heat from the strain gage. If the excitation voltage is too high relative to the heat dissipation characteristics of the material, large changes in temperatures in both the test part and the strain gage can adversely affect the accuracy of the strain measurement. As a result of these, a certain amount of error and uncertainty can be introduced at the very beginning of the measurement process (Tech Note TN-502, Optimizing Strain Gage Excitation Levels ).

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